Primary Transcript Levels Research Articles

Metabolic and circadian inputs encode anticipatory biogenesis of hepatic fed microRNAs.

Starvation and refeeding are mostly unanticipated in the wild in terms of duration, frequency, and nutritional value of the refed state. Notwithstanding this, organisms mount efficient and reproducible responses to restore metabolic homeostasis. Hence, it is intuitive to invoke expectant molecular mechanisms that build anticipatory responses to enable physiological toggling during fed-fast cycles. In this regard, we report anticipatory biogenesis of oscillatory hepatic microRNAs that peak during a fed state and inhibit starvation-responsive genes. Our results clearly demonstrate that the levels of primary and precursor microRNA transcripts increase during a fasting state, in anticipation of a fed response. We delineate the importance of both metabolic and circadian cues in orchestrating hepatic fed microRNA homeostasis in a physiological setting. Besides illustrating metabo-endocrine control, our findings provide a mechanistic basis for the overarching influence of starvation on anticipatory biogenesis. Importantly, by using pharmacological agents that are widely used in clinics, we point out the high potential of interventions to restore homeostasis of hepatic microRNAs, whose deregulated expression is otherwise well established to cause metabolic diseases.

ODP434 Maternally-Derived Pancreatic Extracellular Vesicle Encompassed miRNAs Influence Placental Development in Pregnancies Complicated by Gestational Diabetes

Abstract Pregnancies affected by gestational diabetes (GDM) commonly result in large-for-gestational-age (LGA) infants; these infants have an increased risk of developing cardiometabolic complications compared to appropriate-for-gestational-age (AGA) infants. The mechanisms responsible are unclear but GDM/LGA is associated with altered placental development/function. We have recently reported altered levels of extracellular vesicle (EV) encapsulated miRNAs, including miR-375 (a pancreatic-specific miRNA) in maternal serum prior to the onset of LGA. We propose that the EVs containing miR-375 are produced by maternal pancreas, and that increased miR-375 in maternal circulation contributes to LGA by influencing placental development/function. Human placental tissue was collected from GDM pregnancies that delivered AGA (n=14) or LGA infants (n=10). Levels of mature miR-375 and primary transcript (pri-miR-375) were measured by QPCR. Mature miR-375 was increased in GDM-LGA (4.74-fold; p<0. 01) compared to GDM AGA placentae. Mature miR-375, but not pri-miR-375, was detected in human placenta suggesting that miR-375 is not produced in the placenta but instead is transported, potentially via EVs in maternal circulation. Intact human pancreatic islets (20,000 IEQ/patient) were obtained through the Integrated Islet Distribution Program (IIDP) from female donors of reproductive age. Islets were cultured in EV-depleted media containing 5.5mM (normoglycemia) or 7mM (mild hyperglycaemia) glucose for 3 days. Islet purity and viability were confirmed using dithizone incorporation and trypan blue exclusion, respectively. Media was collected at 24-hour intervals, pooled from all time points, concentrated and EVs were isolated by size exclusion chromatography. Confirmation of the presence of EVs was confirmed by electron microscopy (typical cup-shape morphology of EVs), nanoparticle tracking analysis (NTA; mean size of 83.5-163.2nm; concentration of 1.28×109-1.82×1010 particles/ml), Western blotting (EV-enriched proteins). QPCR confirmed that mature miR-375 was present in islet-derived EVs and revealed that levels were altered following culture in 7mM glucose compared to 5.5mM. Islet-derived EVs were labelled with maleimide-488 and uptake into explants of normal human term placenta was confirmed using fluorescent microscopy=3). miR-375 was overexpressed in normal human placental explants (by 30-fold, p<0. 05; n=6) using specific mimics (100nM for 72 hours) and TMT mass spectrometry was performed to assess the impact of miR-375 overexpression on the placental proteome. Functional enrichment analysis (FEA) was performed on differentially expressed proteins (DEP; P<0. 05; -0.41≥log2foldchange≥0.58) using over representation analysis and Ingenuity Pathway Analysis. This revealed that DEGs were significantly enriched in pathways associated with placental growth, mitochondrial function and glucose metabolism. Our data demonstrates that miR-375 is increased in the placenta in GDM/LGA and that this influences placental development/function. miR-375 does not appear to be produced in the placenta but instead, is likely released in EVs from maternal pancreas under conditions of hyperglycaemia and transported to the placenta, via maternal circulation. This provides insight into the potential mechanisms contributing to LGA in pregnancies complicated by GDM. Presentation: No date and time listed

The Lack of Alternative Oxidase 1a Restricts in vivo Respiratory Activity and Stress-Related Metabolism for Leaf Osmoprotection and Redox Balancing Under Sudden Acute Water and Salt Stress in Arabidopsis thaliana.

In plants salt and water stress result in an induction of respiration and accumulation of stress-related metabolites (SRMs) with osmoregulation and osmoprotection functions that benefit photosynthesis. The synthesis of SRMs may depend on an active respiratory metabolism, which can be restricted under stress by the inhibition of the cytochrome oxidase pathway (COP), thus causing an increase in the reduction level of the ubiquinone pool. However, the activity of the alternative oxidase pathway (AOP) is thought to prevent this from occurring while at the same time, dissipates excess of reducing power from the chloroplast and thereby improves photosynthetic performance. The present research is based on the hypothesis that the accumulation of SRMs under osmotic stress will be affected by changes in folial AOP activity. To test this, the oxygen isotope-fractionation technique was used to study the in vivo respiratory activities of COP and AOP in leaves of wild-type Arabidopsis thaliana plants and of aox1a mutants under sudden acute stress conditions induced by mannitol and salt treatments. Levels of leaf primary metabolites and transcripts of respiratory-related proteins were also determined in parallel to photosynthetic analyses. The lack of in vivo AOP response in the aox1a mutants coincided with a lower leaf relative water content and a decreased accumulation of crucial osmoregulators. Additionally, levels of oxidative stress-related metabolites and transcripts encoding alternative respiratory components were increased. Coordinated changes in metabolite levels, respiratory activities and photosynthetic performance highlight the contribution of the AOP in providing flexibility to carbon metabolism for the accumulation of SRMs.

Upon heat stress processing of ribosomal RNA precursors into mature rRNAs is compromised after cleavage at primary P site in Arabidopsis thaliana

ABSTRACT Transcription and processing of 45S rRNAs in the nucleolus are keystones of ribosome biogenesis. While these processes are severely impacted by stress conditions in multiple species, primarily upon heat exposure, we lack information about the molecular mechanisms allowing sessile organisms without a temperature-control system, like plants, to cope with such circumstances. We show that heat stress disturbs nucleolar structure, inhibits pre-rRNA processing and provokes imbalanced ribosome profiles in Arabidopsis thaliana plants. Notably, the accuracy of transcription initiation and cleavage at the primary P site in the 5’ETS (5’ External Transcribed Spacer) are not affected but the levels of primary 45S and 35S transcripts are, respectively, increased and reduced. In contrast, precursors of 18S, 5.8S and 25S RNAs are rapidly undetectable upon heat stress. Remarkably, nucleolar structure, pre-rRNAs from major ITS1 processing pathway and ribosome profiles are restored after returning to optimal conditions, shedding light on the extreme plasticity of nucleolar functions in plant cells. Further genetic and molecular analysis to identify molecular clues implicated in these nucleolar responses indicate that cleavage rate at P site and nucleolin protein expression can act as a checkpoint control towards a productive pre-rRNA processing pathway.

H2A.B is a cancer/testis factor involved in the activation of ribosome biogenesis in Hodgkin lymphoma.

Testis-specific regulators of chromatin function are commonly ectopically expressed in human cancers, but their roles are poorly understood. Examination of 81 primary Hodgkin lymphoma (HL) samples showed that the ectopic expression of the eutherian testis-specific histone variant H2A.B is an inherent feature of HL. In experiments using two HL cell lines derived from different subtypes of HL, H2A.B knockdown inhibited cell proliferation. H2A.B was enriched in both nucleoli of these HL cell lines and primary HL samples. We found that H2A.B enhanced ribosomal DNA (rDNA) transcription, was enriched at the rDNA promoter and transcribed regions, and interacted with RNA Pol I. Depletion of H2A.B caused the loss of RNA Pol I from rDNA chromatin. Remarkably, H2A.B was also required for high levels of ribosomal protein gene expression being located at the transcriptional start site and within the gene body. H2A.B knockdown reduced gene body chromatin accessibility of active RNA Pol II genes concurrent with a decrease in transcription. Taken together, our data show that in HL H2A.B has acquired a new function, the ability to increase ribosome biogenesis.

High Expression of ERK-related RASGRF2 predicts Poor prognosis in patients with Stomach Adenocarcinoma and correlates with M2 macrophage.

Background: The role of RASGRF2 has been verified in the development of various cancers. However, its roles in stomach adenocarcinoma (STAD) are still under investigation.Methods: RASGRF2 transcript-level data and the associated clinical information from patients with STAD were extracted from The Cancer Genome Atlas (TCGA). Diagnostic and prognostic values of RASGRF2 were analyzed using receiver-operator characteristics (ROC) analysis, correlation analysis, and survival analysis in conjunction with a prognostic model. In addition, gene expression profiles, differentially-expressed genes for co-varying expression, and a differential expressed genes (DEG) protein-protein interaction network for influential nodes were also analyzed. To identify the molecular role of RASGRF2 in STAD, gene ontology (GO) term, Kyoto Encyclopedia of Genes and Genomes (KEGG) biological pathway, and gene set enrichment analysis (GSEA)-mediated functional module enrichment analyses were conducted. The relationship between RASGRF2 and gene signature-based predicted immune cell infiltration patterns were also investigated. To validate the bioinformatic findings, RASGRF2 protein expression was investigated in vitro using western blot and immunohistochemistry. Furthermore, relationships among RASGRF2 protein expression, clinicopathologic characteristics, and patient survival were analyzed.Results: Bioinformatic analysis revealed a significantly higher RASGRF2 transcript level in STAD tissue, which was positively associated with the T stage, histological type, histological grade, and TP53 status. Moreover, the RASGRF2 transcript level indicated poor overall survival in STAD patients (hazard ratio = 1.47, P = 0.023). Multivariate Cox regression analysis showed that primary therapy outcome, age, and RASGRF2 transcript level were independent prognostic factors for survival, and the C-index of a nomogram was 0.695. Additionally, 159 genes were differentially expressed according to RASGRF2 transcript levels; 15 exhibited co-varying expression, and 13 were identified as influential nodes. The DEG-list was significantly enriched for several GO terms, biological pathways, and functional modules, including MAPK, RAS, ERK, and immunoregulatory pathways. RASGRF2 transcript levels were significantly positively correlated with infiltration levels of Tem, Macrophages, pDCs, and NK cells. Validation analysis showed similar results for the RASGRF2 protein expression level in both in vitro analyses.Conclusion: Bioinformatic predictions combined with in vitro validation suggest that RASGRF2 plays diagnostic and prognostic roles and serves as a negative protective molecular factor in STAD patients.

Two distinct nucleic acid binding surfaces of Cdc5 regulate development.

Cell division cycle 5 (Cdc5) is a highly conserved nucleic acid binding protein among eukaryotes and plays critical roles in development. Cdc5 can simultaneously bind to DNA and RNA by its N-terminal DNA-binding domain (DBD), but molecular mechanisms describing its nucleic acid recognition and the regulation of development through its nucleic acid binding remain unclear. Herein, we present a crystal structure of the N-terminal DBD of MoCdc5 (MoCdc5-DBD) from the rice blast fungus Magnaporthe oryzae. Residue K100 of MoCdc5 is on the periphery of a positively charged groove that is formed by K42, K45, R47, and N92 and is evolutionally conserved. Mutation of K100 significantly reduces the affinity of MoCdc5-DBD to a Cdc5-binding element but not to a conventional myeloblastosis (Myb) domain-binding element, suggesting that K100 is a key residue of the high binding affinity to Cdc5-binding element. Another conserved residue (R31) is located close to the U6 RNA in the structure of the spliceosome, and its mutation dramatically reduces the binding capacity of MoCdc5-DBD for U6 RNA. Importantly, mutations in these key residues, including R31, K42, and K100 in AtCDC5, an Arabidopsis thaliana ortholog of MoCdc5, greatly impair the functions of AtCDC5, resulting in pleiotropic development defects and reduced levels of primary microRNA transcripts. Taken together, our findings suggest that Cdc5-DBD binds nucleic acids with two distinct binding surfaces, one for DNA and another for RNA, which together contribute to establishing the regulation mechanism of Cdc5 on development through nucleic acid binding.

Novel Mechanisms for IGF-I Regulation by Glucagon in Carp Hepatocytes: Up-Regulation of HNF1α and CREB Expression via Signaling Crosstalk for IGF-I Gene Transcription.

Glucagon, a key hormone for glucose homeostasis, can exert functional crosstalk with somatotropic axis via modification of IGF-I expression. However, its effect on IGF-I regulation is highly variable in different studies and the mechanisms involved are largely unknown. Using grass carp as a model, the signal transduction and transcriptional mechanisms for IGF-I regulation by glucagon were examined in Cyprinid species. As a first step, the carp HNF1α, a liver-enriched transcription factor, was cloned and confirmed to be a single-copy gene expressed in the liver. In grass carp hepatocytes, glucagon treatment could elevate IGF-I, HNF1α, and CREB mRNA levels, induce CREB phosphorylation, and up-regulate HNF1α and CREB protein expression. The effects on IGF-I, HNF1α, and CREB gene expression were mediated by cAMP/PKA and PLC/IP3/PKC pathways with differential coupling with the MAPK and PI3K/Akt cascades. During the process, protein:protein interaction between HNF1α and CREB and recruitment of RNA Pol-II to IGF-I promoter also occurred with a rise in IGF-I primary transcript level. In parallel study to examine grass carp IGF-I promoter activity expressed in αT3 cells, similar pathways for post-receptor signaling were also confirmed in glucagon-induced IGF-I promoter activation and the trans-activating effect by glucagon was mediated by the binding sites for HNF1α and CREB located in the proximal region of IGF-I promoter. Our findings, as a whole, shed light on a previously undescribed mechanism for glucagon-induced IGF-I gene expression by increasing HNF1α and CREB production via functional crosstalk of post-receptor signaling. Probably, by protein:protein interaction between the two transcription factors and subsequent transactivation via their respective cis-acting elements in the IGF-I promoter, IGF-I gene transcription can be initiated by glucagon at the hepatic level.

Do Arabidopsis Squamosa promoter binding Protein-Like genes act together in plant acclimation to copper or zinc deficiency?

The genome of Arabidopsis thaliana encodes approximately 260 copper (Cu)‐dependent proteins, which includes enzymes in central pathways of photosynthesis, respiration and responses to environmental stress. Under Cu‐deficient growth conditions, Squamosa promoter binding Protein‐Like 7 (SPL7) activates the transcription of genes encoding Cu acquisition systems, and it mediates a metabolic reorganization to economize on Cu. The transcription factor SPL7 groups among comparably large proteins in the SPL family, which additionally comprises a second group of small SPL proteins targeted by miRNA156 with roles in plant development. SPL7 shares extended regions of sequence homology with SPL1 and SPL12. Therefore, we investigated the possibility of a functional overlap between these three members of the group of large SPL family proteins. We compared the spl1 spl12 double mutant and the spl1 spl7 spl12 triple mutant with both the wild type and the spl7 single mutant under normal and Cu‐deficient growth conditions. Biomass production, chlorophyll content and tissue elemental composition at the seedling stage, as well as plant and flower morphology during reproductive stages, confirmed the involvement of SPL7, but provided no indication for important roles of SPL1 or SPL12 in the acclimation of Arabidopsis to Cu deficiency. Furthermore, we analyzed the effects of zinc (Zn) deficiency on the same set of mutants. Different from what is known in the green alga Chlamydomonas reinhardtii, Arabidopsis did not activate Cu deficiency responses under Zn deficiency, and there was no Cu overaccumulation in either shoot or root tissues of Zn‐deficient wild type plants. Known Zn deficiency responses were unaltered in spl7, spl1 spl12 and spl1 spl7 spl12 mutants. We observed that CuZnSOD activity is strongly downregulated in Zn‐deficient A. thaliana, in association with an about 94% reduction in the abundance of the CSD2 transcript, a known target of miR398. However, different from the known Cu deficiency responses of Arabidopsis, this Zn deficiency response was independent of SPL7 and not associated with an upregulation of MIR398b primary transcript levels. Our data suggest that there is no conservation in A. thaliana of the crosstalk between Zn and Cu homeostasis mediated by the single SPL family protein CRR1 of Chlamydomonas. In the future, resolving how the specificity of SPL protein activation and recognition of target gene promoters is achieved will advance our understanding of the specific functions of different SPL family proteins in the regulation of either Cu deficiency responses or growth and development of land plants.

Put the Pedal to the METTL1: Adding Internal m7G Increases mRNA Translation Efficiency and Augments miRNA Processing.

Complementary papers by Zhang, Liu, and colleagues (Zhang etal., 2019) and Pandolfini, Barbieri, and colleagues (Pandolfini etal., 2019) develop new sequencing techniques that reveal that METTL1 N7-methylates internal guanosines in mRNAs and miRNAs to increase translation efficiency and miRNA processing, respectively.

Biological and RNA regulatory function of MOV10 in mammalian germ cells

BackgroundRNA regulation by RNA-binding proteins (RBPs) involve extremely complicated mechanisms. MOV10 and MOV10L1 are two homologous RNA helicases implicated in distinct intracellular pathways. MOV10L1 participates specifically in Piwi-interacting RNA (piRNA) biogenesis and protects mouse male fertility. In contrast, the functional complexity of MOV10 remains incompletely understood, and its role in the mammalian germline is unknown. Here, we report a study of the biological and molecular functions of the RNA helicase MOV10 in mammalian male germ cells.ResultsMOV10 is a nucleocytoplasmic protein mainly expressed in spermatogonia. Knockdown and transplantation experiments show that MOV10 deficiency has a negative effect on spermatogonial progenitor cells (SPCs), limiting proliferation and in vivo repopulation capacity. This effect is concurrent with a global disturbance of RNA homeostasis and downregulation of factors critical for SPC proliferation and/or self-renewal. Unexpectedly, microRNA (miRNA) biogenesis is impaired due partially to decrease of miRNA primary transcript levels and/or retention of miRNA via splicing control. Genome-wide analysis of RNA targetome reveals that MOV10 binds preferentially to mRNAs with long 3′-UTR and also interacts with various non-coding RNA species including those in the nucleus. Intriguingly, nuclear MOV10 associates with an array of splicing factors, particularly with SRSF1, and its intronic binding sites tend to reside in proximity to splice sites.ConclusionsThese data expand the landscape of MOV10 function and highlight a previously unidentified role initiated from the nucleus, suggesting that MOV10 is a versatile RBP involved in a broader RNA regulatory network.

ORAI1/STIM1 Interaction Intervenes in Stroke and in Neuroprotection Induced by Ischemic Preconditioning Through Store-Operated Calcium Entry.

Background and Purpose- Disturbance of endoplasmic reticulum (ER) Ca2+ homeostasis causes neuronal cell injury in stroke. By contrast, ischemic preconditioning (IPC)-a brief sublethal ischemic episode affording tolerance to a subsequent ischemic insult-restores ER Ca2+ homeostasis. Under physiological conditions, ER calcium content is continuously refilled by the interaction between the ER-located Ca2+ sensor STIM (stromal interacting molecule) 1 and the plasma membrane channel ORAI1 (a structural component of the CRAC calcium channel)-2 key mediators of the store-operated calcium entry (SOCE) mechanism. However, the role played by ORAI1 and STIM1 in stroke and in IPC-induced neuroprotection during stroke remains unknown. Therefore, we explored whether ORAI1 and STIM1 might be involved in stroke pathogenesis and in IPC-induced neuroprotection. Methods- Primary cortical neurons were subjected to oxygen and glucose deprivation+reoxygenation to reproduce in vitro brain ischemia. Focal brain ischemia and IPC were induced in rats by transient middle cerebral artery occlusion. Expression of ORAI1 and STIM1 transcripts and proteins and their immunosignals were detected by qRT-PCR, Western blot, and immunocytochemistry, respectively. SOCE and Ca2+ release-activated Ca2+ currents (ICRAC) were measured by Fura-2 AM video imaging and patch-clamp electrophysiology in whole-cell configuration, respectively. Results- STIM1 and ORAI1 protein expression and immunosignals decreased in the ipsilesional temporoparietal cortex of rats subjected to transient middle cerebral artery occlusion followed by reperfusion. Analogously, in primary hypoxic cortical neurons, STIM1 and ORAI1 transcript and protein levels decreased concurrently with SOCE and Ca2+ release-activated Ca2+currents. By contrast, IPC induced SOCE and Ca2+ release-activated Ca2+current upregulation, thereby preventing STIM1 and ORAI1 downregulation induced by oxygen and glucose deprivation+reoxygenation. Silencing of STIM1 or ORAI1 prevented IPC-induced tolerance and caused ER stress, as measured by GRP78 (78-kDa glucose regulated protein) and caspase-3 upregulation. Conclusions- ORAI1 and STIM1, which participate in SOCE, take part in stroke pathophysiology and play an important role in IPC-induced neuroprotection.

SUN-471 Corresponding Primary Transcript and mRNA Levels for Pomc and Prss56 Suggest Oscillating Transcriptions in Adult Rat Tanycytes

We recently reported mRNA and protein expression patterns in adult rat hypothalamic tanycytes that suggest oscillatory gene expression, demonstrating highly variable pro-opiomelanocortin (Pomc) mRNA and protein expression in these cells with 40% of rats expressing high, 40% low, and another 20% intermediate levels (Wittmann et al., J Comp Neurol, 2017). In addition, we demonstrated that mRNA expression for Prss56 , a trypsin-like serine protease, is comparably variable but inversely proportional to that of Pomc in tanycytes (Wittmann and Lechan, J Comp Neurol, 2018), proposing that the most likely explanation for this variability is that the two genes are expressed in an out-of-phase, oscillatory manner. Since the amount of mRNA depends on both the rate of transcription and mRNA degradation, we investigated whether increased transcription drives the accumulation of Pomc and Prss56 mRNAs. Fluorescent in situ hybridization was used to detect Pomc and Prss56 primary transcripts (hnRNA) using probes against intronic sequences. As expected, intronic hybridization signal was localized in nuclei rather than the cytoplasm; while Prss56 primary transcript was represented by only 1 or 2 intensely fluorescent nuclear dots, the hybridization signal for Pomc primary transcript ranged from a single dot to filling the entire nucleus. A high correlation was found between the expression levels of primary transcripts and the respective mRNAs. In general, high Pomc or Prss56 mRNA levels were accompanied by high Pomc or Prss56 hnRNA levels in tanycytes, whereas low hnRNA levels corresponded to low mRNA levels. These data indicate that variable Pomc and Prss56 mRNA levels highly correlate with the transcriptional activity of these genes, raising the possibility of oscillatory expression and/or activity of certain transcription factors in adult rat tanycytes. We hypothesize that this phenomenon may be related to the stem/progenitor cell function of tanycytes (Prevot et al., Endocr Rev, 2018) and reminiscent of the oscillatory expression of transcription factors in neural progenitor cells during development (Kageyama et al., Neurosci Res, 2018).

MAC3A and MAC3B, Two Core Subunits of the MOS4-Associated Complex, Positively Influence miRNA Biogenesis.

MAC3A and MAC3B are conserved U-box-containing proteins in eukaryotes. They are subunits of the MOS4-associated complex (MAC) that plays essential roles in plant immunity and development in Arabidopsis thaliana However, their functional mechanisms remain elusive. Here, we show that Arabidopsis MAC3A and MAC3B act redundantly in microRNA (miRNA) biogenesis. Lack of both MAC3A and MAC3B in the mac3b mac3b double mutant reduces the accumulation of miRNAs, causing elevated transcript levels of miRNA targets. mac3a mac3b also decreases the levels of primary miRNA transcripts (pri-miRNAs). However, MAC3A and MAC3B do not affect the promoter activity of genes encoding miRNAs (MIR genes), suggesting that they may not affect MIR transcription. This result, together with the fact that MAC3A associates with pri-miRNAs in vivo, indicates that MAC3A and MAC3B may stabilize pri-miRNAs. Furthermore, we find that MAC3A and MAC3B interact with the DCL1 complex that catalyzes miRNA maturation, promote DCL1 activity, and are required for the localization of HYL1, a component of the DCL1 complex. Besides MAC3A and MAC3B, two other MAC subunits, CDC5 and PRL1, also function in miRNA biogenesis. Based on these results, we propose that MAC functions as a complex to control miRNA levels through modulating pri-miRNA transcription, processing, and stability.

Lin-4 and the NRDE pathway are required to activate a transgenic lin-4 reporter but not the endogenous lin-4 locus in C. elegans.

As the founding member of the microRNA (miRNA) gene family, insights into lin-4 regulation and function have laid a conceptual foundation for countless miRNA-related studies that followed. We previously showed that a transcriptional lin-4 reporter in C. elegans was positively regulated by a lin-4-complementary element (LCE), and by lin-4 itself. In this study, we sought to (1) identify additional factors required for lin-4 reporter expression, and (2) validate the endogenous relevance of a potential positive autoregulatory mechanism of lin-4 expression. We report that all four core nuclear RNAi factors (nrde-1, nrde-2, nrde-3 and nrde-4), positively regulate lin-4 reporter expression. In contrast, endogenous lin-4 levels were largely unaffected in nrde-2;nrde-3 mutants. Further, an endogenous LCE deletion generated by CRISPR-Cas9 revealed that the LCE was also not necessary for the activity of the endogenous lin-4 promoter. Finally, mutations in mature lin-4 did not reduce primary lin-4 transcript levels. Taken together, these data indicate that under growth conditions that reveal effects at the transgenic locus, a direct, positive autoregulatory mechanism of lin-4 expression does not occur in the context of the endogenous lin-4 locus.

Modes of action of squamocin in the anal papillae of Aedes aegypti larvae

The morphological and the primary transcript levels of the genes for aquaporin AaAQP4 and the membrane transporter AaV-H+-ATPase in the anal papillae of A. aegypti larvae exposed to squamocin were evaluated. Squamocin caused great vacuolization in the anal papillae wall, basal lamina disruption with loss of canalicular spaces, and disorganization of the cuticular layers. There was also decrease of AaAQP4 transcript levels and inhibition of AaV-H+-ATPase in the anal papillae of larvae. Morphological together with decrease in the AaAQP4 and AaV-H+-ATPase primary transcript levels suggest that squamocin may affect osmoregulation and ion-regulation of this insect followed by death.

GM-CSF and IL-3 Modulate Human Monocyte TNF-α Production and Renewal in In Vitro Models of Trained Immunity.

GM-CSF and IL-3 are hematopoietic cytokines that also modulate the effector functions of several immune cell subsets. In particular, GM-CSF and IL-3 exert a significant control on monocyte and macrophage effector functions, as assessed in experimental models of inflammatory and autoimmune diseases and also in human studies. Here, we sought to investigate the mechanisms and the extent to which GM-CSF and IL-3 modulate the pro-inflammatory, LPS-mediated, activation of human CD14+ monocytes taking into account the new concept of trained immunity (i.e., the priming stimulus modulates the response to subsequent stimuli mainly by inducing chromatin remodeling and increased transcription at relevant genetic loci). We demonstrate that GM-CSF and IL-3 priming enhances TNF-α production upon subsequent LPS stimulation (short-term model of trained immunity) in a p38- and SIRT2-dependent manner without increasing TNF primary transcript levels (a more direct measure of transcription), thus supporting a posttranscriptional regulation of TNF-α in primed monocytes. GM-CSF and IL-3 priming followed by 6 days of resting also results in increased TNF-α production upon LPS stimulation (long-term model of trained immunity). In this case, however, GM-CSF and IL-3 priming induces a c-Myc-dependent monocyte renewal and increase in cell number that is in turn responsible for heightened TNF-α production. Overall, our results provide insights to understand the biology of monocytes in health and disease conditions in which the hematopoietic cytokines GM-CSF and IL-3 play a role and also extend our knowledge of the cellular and molecular mechanisms of trained immunity.

MicroRNA-126 is Dysregulated in Cancer- Free Females Harboring Methylated BRCA1 Promoter through Up-Regulation of DNMTs

Background: Numerous microRNAs have been categorized as tumor suppressors that are often repressed by aberrant DNA methylation. Recently, BRCA1 promoter methylation in White Blood Cells (WBC) has been linked to elevated risk of developing breast cancer. In the present study, we aimed to investigative cancerrelated microRNA alterations in WBC harboring methylated BRCA1 promoter. Methods: The Human Cancer miRNA EpiTect Methyl II Signature PCR Array was used to study the methylation status of several cancer-related microRNA sequences. Real time RT-PCR was used to determine the levels of microRNA primary transcripts and DNMTs. The Stem-loop RT-PCR assay was also used to quantify the expression levels of mature microRNAs. Results: Out of 35 miRNAs, miR-126 was found to be hyper-methylated in WBC of breast cancer patients as well as in WBC of cancer-free females who harbored methylated BRCA1 (carriers). The methylation was associated with down regulation of the pre-miR-126 in WBC and lower levels of circulating mature miR-126 in the plasma. Strong positive correlation between the expression levels of both forms of miR-126s was observed in the carriers but not in cancer patients. Importantly, we have found higher mRNA expression of DNMT1, DNMT3a and DNMT3b in WBC of carriers compared to controls. Conclusion: Here, we have demonstrated that miR-126 is dysregulated in WBC of cancer-free females harboring methylated BRCA1 promoter. Importantly, our findings suggest that the up-regulation of DNMTs could be responsible for the aberrant methylation of both miR-126 and BRCA1 promoter in WBC.

Orchestrating Developmental Signaling to Balance Erythroblast Proliferation and Differentiation

The highly conserved exosome complex mediates the degradation and processing of multiple classes of RNAs. How this post-transcriptional RNA- and gene-regulatory machine impacts cell fate decisions and differentiation is poorly understood. Previously, we demonstrated that exosome complex subunits confer an erythroid maturation barricade, and the erythroid transcription factor GATA-1 dismantles the barricade by transcriptionally repressing the cognate genes. While dissecting requirements for the maturation barricade in mice, we discovered that the exosome complex is a vital determinant of a developmental signaling transition that dictates proliferation versus differentiation of erythroid precursor cells. Using shRNAs to downregulate exosome complex subunits, we developed conditions that disrupt exosome complex integrity and analyzed functional consequences. We discovered that erythroid precursor cells derived from E14.5 murine fetal liver exhibited significantly decreased survival when erythropoietin (Epo) was removed from the culture media. Live cells decreased from 66% in the control to 24% (p = 2 x 10-5) in the Exosc8-knockdown condition. The maturation-associated increase (1.5 fold, p = 0.003) in the Ter119+CD71+ (R3: early/late basophilic erythroblast) population upon Exosc8 knockdown did not occur without exogenous Epo. Thus, the survival and differentiation of erythroid precursors after downregulating Exosc8 is critically dependent on Epo. We tested whether Exosc8 downregulation impaired stem cell factor (SCF)-mediated proliferation/amplification of erythroid precursors. Using a phospho-flow cytometry assay, we quantitated the capacity of SCF or Epo to instigate cell signaling using the shared downstream substrate Akt. SCF induced maximal Akt phosphorylation in immature Ter119-CD71high erythroblasts (5.5 fold, p = 3 x 10-6). As erythroid maturation progressed to Ter119+CD71high, the SCF response was diminished. Exosc8 downregulation abrogated SCF-mediated induction of phospho-Akt. Epo induced maximal Akt phosphorylation in Ter119+CD71high erythroblasts, and Exosc8 downregulation accelerated acquisition of this signaling response. Whereas Epo did not affect Akt phosphorylation in control Ter119-CD71high erythroblasts, Epo increased phospho-Akt 4 fold (p = 0.003) upon Exosc8 downregulation. Thus, downregulating Exosc8 abrogated SCF signaling that supports erythroid precursor proliferation/amplification, while precociously inducing Epo-dependent pro-differentiation signaling. As downregulating Exosc8 abrogated SCF signaling, we tested whether the exosome complex or individual subunits confer Kit expression or promote signaling via a post-receptor mechanism. Downregulating Exosc8 or Exosc9 reduced Kit surface expression in the R2 (proerythroblast and early basophilic) cell population [14.6 (p = 3.6 x 10-4) and 6 fold (p= 1.3 x 10-6) decrease, respectively]. Exosc8 downregulation also reduced Kit mRNA and primary transcript levels at all erythroid maturation stages. By 24 h post-infection with shExosc8-expressing retrovirus, Kit protein decreased 10 fold (p = 0.046) in Ter119- erythroid precursor cells. We tested whether the Exosc8 requirement for Kit primary transcript, mRNA and protein expression involved alterations in the distribution of transcriptionally-competent serine 5-phosphorylated RNA polymerase II (Pol II) at Kit. Using quantitative ChIP analysis with control and Exosc8-knockdown Ter119- cells, Exosc8 downregulation reduced phospho-Ser5 Pol II occupancy within the coding region (+5 kb) and 3' UTR, but not at the promoter. Furthermore, Exosc9 occupied multiple regions of the Kit locus. These results support a model in which the exosome complex confers Kit expression and stem cell factor/Kit signaling via a transcriptional mechanism. Functioning as a gatekeeper of the SCF - Epo developmental signaling transition, the exosome complex controls the massive production of erythroid cells that ensures organismal survival in homeostatic and stress contexts. Studies are underway to establish the full repertoire of exosome complex targets in the developing erythroblast, how these targets relate to exosome complex targets in hematopoietic stem and progenitor cells and exosome complex-dependent strategies for translational applications. DisclosuresNo relevant conflicts of interest to declare.

SnRNA 3' End Processing by a CPSF73-Containing Complex Essential for Development in Arabidopsis.

Uridine-rich small nuclear RNAs (snRNAs) are the basal components of the spliceosome and play essential roles in splicing. The biogenesis of the majority of snRNAs involves 3′ end endonucleolytic cleavage of the nascent transcript from the elongating DNA-dependent RNA ploymerase II. However, the protein factors responsible for this process remain elusive in plants. Here, we show that DEFECTIVE in snRNA PROCESSING 1 (DSP1) is an essential protein for snRNA 3′ end maturation in Arabidopsis. A hypomorphic dsp1-1 mutation causes pleiotropic developmental defects, impairs the 3′ end processing of snRNAs, increases the levels of snRNA primary transcripts (pre-snRNAs), and alters the occupancy of Pol II at snRNA loci. In addition, DSP1 binds snRNA loci and interacts with Pol-II in a DNA/RNA-dependent manner. We further show that DSP1 forms a conserved complex, which contains at least four additional proteins, to catalyze snRNA 3′ end maturation in Arabidopsis. The catalytic component of this complex is likely the cleavage and polyadenylation specificity factor 73 kDa-I (CSPF73-I), which is the nuclease cleaving the pre-mRNA 3′ end. However, the DSP1 complex does not affect pre-mRNA 3′ end cleavage, suggesting that plants may use different CPSF73-I-containing complexes to process snRNAs and pre-mRNAs. This study identifies a complex responsible for the snRNA 3′ end maturation in plants and uncovers a previously unknown function of CPSF73 in snRNA maturation.