mRNA Decay Research Articles

Stalled disomes marked by Hel2-dependent ubiquitin chains undergo Ubp2/Ubp3-mediated deubiquitination upon translational run-off

Stalled ribosomes cause collisions, impair protein synthesis, and generate potentially harmful truncated polypeptides. Eukaryotic cells utilize the ribosome-associated quality control (RQC) and no-go mRNA decay (NGD) pathways to resolve these problems. In yeast, the E3 ubiquitin ligase Hel2 recognizes and polyubiquitinates disomes and trisomes at the 40S ribosomal protein Rps20/uS10, thereby priming ribosomes for further steps in the RQC/NGD pathways. Recent studies have revealed high concentrations of disomes and trisomes in unstressed cells, raising the question of whether and how Hel2 selects long-term stalled disomes and trisomes. This study presents quantitative analysis of in vivo-formed Hel2•ribosome complexes and the dynamics of Hel2-dependent Rps20 ubiquitination and Ubp2/Ubp3-dependent deubiquitination. Our findings show that Hel2 occupancy progressively increases from translating monosomes to disomes and trisomes. We demonstrate that disomes and trisomes with mono- or di-ubiquitinated Rps20 resolve independently of the RQC component Slh1, while those with tri- and tetra-ubiquitinated Rps20 do not. Based on the results, we propose a model in which Hel2 translates the duration of ribosome stalling into polyubiquitin chain length. This mechanism allows for the distinction between transient and long-term stalling, providing the RQC machinery with a means to select fatally stalled ribosomes over transiently stalled ones.

CircPRKD3-loaded exosomes concomitantly elicit tumor growth inhibition and glioblastoma microenvironment remodeling via inhibiting STAT3 signaling.

Glioblastoma stem cells (GSCs) and their exosomes (exos) are involved in shaping the immune microenvironment, which is important for tumor invasion and recurrence. However, studies involving GSC-derived exosomal circular RNAs (GDE-circRNAs) in regulating tumor microenvironment (TME) remain unknown. Here, we comprehensively evaluated the significance of a novel immune-related GDE-circRNA in glioma microenvironment. GDE-circPRKD3 was screened out through high-throughput sequencing and verified by RT-PCR, sanger sequencing and RNase R assays. A series of in vitro and in vivo experiments were performed to investigate the function of GDE-circPRKD3. RNA-seq, RNA immunoprecipitation, multicolor flow cytometry and western blotting were used to explore the regulation of GDE-circPRKD3 on STAT3 signaling-mediated TME remodeling. We have characterized a circRNA PRKD3 in GSC exosomes, and lower circPRKD3 expression predicts a worse prognosis for glioblastoma patients. Overexpression of GDE-circPRKD3 significantly impairs the biological competence of glioma and prolongs the survival of xenograft mice. GDE-circPRKD3 binds to HNRNPC in an m6A-dependent manner, accelerates mRNA decay of IL6ST and inhibits downstream target STAT3. Notably, GDE-circPRKD3 promotes CXCL10 secretion by reprogramming tumor-associated macrophages, which in turn recruits CD8+ tumor infiltrating lymphocytes against GBM. Moreover, brain-targeted lipid nanoparticle delivery of circPRKD3 combined with immune checkpoint blockade therapy achieves significant combinatorial benefits. This study provides a novel mechanism by which GDE-circPRKD3 relies on STAT3 signaling to remodel immunosuppressive TME and offers a potential RNA immunotherapy strategy for GBM treatment.

Cytoplasmic mRNA decay and quality control machineries in eukaryotes.

mRNA degradation pathways have key regulatory roles in gene expression. The intrinsic stability of mRNAs in the cytoplasm of eukaryotic cells varies widely in a gene- and isoform-dependent manner and can be regulated by cellular cues, such as kinase signalling, to control mRNA levels and spatiotemporal dynamics of gene expression. Moreover, specialized quality control pathways exist to rid cells of non-functional mRNAs produced by errors in mRNA processing or mRNA damage that negatively impact translation. Recent advances in structural, single-molecule and genome-wide methods have provided new insights into the central machineries that carry out mRNA turnover, the mechanisms by which mRNAs are targeted for degradation and the general principles that govern mRNA stability at a global level. This improved understanding of mRNA degradation in the cytoplasm of eukaryotic cells is finding practical applications in the design of therapeutic mRNAs.

Cytoplasmic mRNA decay controlling inflammatory gene expression is determined by pre-mRNA fate decision.

The fidelity of immune responses depends on timely controlled and selective mRNA degradation that is largely driven by RNA-binding proteins (RBPs). It remains unclear whether stochastic or directed processes govern the selection of an individual mRNA molecule for degradation. Using human and mouse cells, we show that tristetraprolin (TTP, also known as ZFP36), an essential anti-inflammatory RBP, destabilizes target mRNAs via a hierarchical molecular assembly. The assembly formation strictly relies on the interaction of TTP with RNA. The TTP homolog ZFP36L1 exhibits similar requirements, indicating a broader relevance of this regulatory program. Unexpectedly, the assembly of the cytoplasmic mRNA-destabilization complex is licensed in the nucleus by TTP binding to pre-mRNA, which we identify as the principal TTP target rather than mRNA. Hence, the fate of an inflammation-induced mRNA is decided concomitantly with its synthesis. This mechanism prevents the translation of excessive and potentially harmful inflammation mediators, irrespective of transcription.

Reduced UPF1 levels in senescence impair nonsense-mediated mRNA decay

Cells regulate gene expression through various RNA regulatory mechanisms, and this regulation often becomes less efficient with age, contributing to accelerated aging and various age-related diseases. Nonsense-mediated mRNA decay (NMD), a well-characterized RNA surveillance mechanism, degrades aberrant mRNAs with premature termination codons (PTCs) to prevent the synthesis of truncated proteins. While the role of NMD in cancer and developmental and genetic diseases is well documented, its implications in human aging remain largely unexplored. This study reveals a significant decline in the levels of the protein UPF1, a key player in NMD, during cellular senescence. Additionally, NMD substrates accumulate in senescent cells, along with decreased levels of cap-binding protein 80/20 (CBP80/20)-dependent translation (CT) factors and reduced binding to active polysomes, indicating reduced efficiency of NMD. Moreover, knockdown of UPF1 in proliferating WI-38 cells induces senescence, as evidenced by increased senescence-associated β-galactosidase activity, alterations in senescence-associated molecular markers, increased endogenous γ-H2AX levels, and reduced cell proliferation. These findings suggest that the decline in UPF1 levels during cellular senescence accelerates the senescent phenotype by impairing NMD activity and the consequent accumulation of abnormal mRNA.

IRE1 is a Promising Therapeutic Target in Pancreatic Cancer.

Pancreatic cancer (PC) is one of the most aggressive malignancies, characterized by an increasing incidence and unfavorable prognosis. Despite recent advances, surgical resection combined with chemotherapy remains the only potentially curative therapeutic option. Therefore, it is of paramount importance to identify novel therapeutic targets and develop effective treatment strategies. Pancreatic ductal adenocarcinoma (PDAC), the most prevalent form of PC, originates from exocrine cells and is subjected to both intrinsic and extrinsic cellular stresses, including oncogene activation, loss of tumor suppressors, a hypoxic and immunosuppressive tumor microenvironment (TME), and chemotherapy, causing an accumulation of misfolded proteins within the endoplasmic reticulum (ER). The loss of ER proteostasis activates the unfolded protein response (UPR), an intracellular sensing-signaling network that enables cancer cells to alleviate ER stress and restore cellular proteostasis. The key UPR sensor Inositol-Requiring Enzyme 1 (IRE1) is an ER membrane protein that activates the transcription factor X-Box Protein 1 Spliced (XBP1s) through its cytoplasmic kinase-RNase module, promoting protein folding, secretion capacity, and proteasomal degradation of misfolded proteins. Additionally, it regulates IRE1-dependent decay (RIDD) of various mRNA and functions through scaffold interactions. In this review, we synthesize current evidence on the cell-autonomous and cell-non-autonomous roles of IRE1 in tumor initiation, progression, metastasis, and drug resistance in PDAC and outline key research directions to investigate IRE1 as a potential therapeutic target.

AGD1/USP10/METTL13 complexes enhance cancer stem cells proliferation and diminish the therapeutic effect of docetaxel via CD44 m6A modification in castration resistant prostate cancer

BackgroundMost patients with prostate cancer inevitably progress to castration-resistant prostate cancer (CRPC), at which stage chemotherapeutics like docetaxel become the first-line treatment. However, chemotherapy resistance typically develops after an initial period of therapeutic efficacy. Increasing evidence indicates that cancer stem cells confer chemotherapy resistance via exosomes. This study demonstrated that AGD1, derived from prostate cancer stem cells (PCSCs), enhanced the stemness of prostate cancer cells and reduced the therapeutic effect of docetaxel in CRPC.MethodsQuantitative real-time PCR (qPCR) was employed to determine the expression levels of AGD1 and METTL13 mRNAs in PCSCs and exosomes. Protein expression levels were examined using western blots and dot blots. The potential functions of AGD1 and METTL13 in CRPC were investigated through cell proliferation assay, Transwell assay, EdU incorporation assays, Annexin V-FITC/PI staining, and sphere formation assays. To uncover the underlying mechanisms of AGD1, RNA pull-down assay, RIP, co-Immunoprecipitation (co-IP), mass spectrometry (MS), Methylated RNA immunoprecipitation (MeRIP) and single-base elongation and ligation-based qPCR amplification method (SELECT) were performed. The effects of AGD1 and METTL13 on CRPC development and metastasis under docetaxel treatment were analyzed using a xenograft mouse model and an organoid model. Additionally, liposomal-chitosan nanocomplex drug delivery systems were designed to explore AGD1’s role in regulating docetaxel treatment resistance in CRPC.ResultsAGD1 expression was upregulated in PCSCs and exosomes. Downregulating AGD1 enhanced the sensitivity of CRPC to docetaxel treatment by inhibiting their stemness, with the reverse also being true. RNA pull-down, combined with MS, co-IP and RIP assays, demonstrated that AGD1 binds to METTL13 and USP10, forming a complex that facilitates METTL13 protein accumulation through USP10-induced deubiquitination. MeRIP assay and SELECT assay revealed that METTL13 transcriptionally controls the mRNA decay of CD44 via m6A methylation. Additionally, this process activates the pSTAT3/PI3K-AKT signaling pathway. Organoid models and liposomal-chitosan nanocomplex drug delivery systems showed that reducing AGD1 expression enhanced the therapeutic effect of docetaxel in CRPC.ConclusionsAGD1 mediates the stemness and apoptosis of PCSCs and promotes docetaxel treatment resistance by enhancing tumor growth and metastasis through USP10/METTL13-mediated CD44 mRNA decay in CRPC.

ADARp110 promotes hepatocellular carcinoma progression via stabilization of CD24 mRNA

ADAR is highly expressed and correlated with poor prognosis in hepatocellular carcinoma (HCC), yet the role of its constitutive isoform ADARp110 in tumorigenesis remains elusive. We investigated the role of ADARp110 in HCC and underlying mechanisms using clinical samples, a hepatocyte-specific Adarp110 knock-in mouse model, and engineered cell lines. ADARp110 is overexpressed and associated with poor survival in both human and mouse HCC. It creates an immunosuppressive microenvironment by inhibiting total immune cells, particularly cytotoxic GZMB+CD8+ T cells infiltration, while augmenting Treg cells, MDSCs, and exhausted CD8+ T cells ratios. Mechanistically, ADARp110 interacts with SNRPD3 and RNPS1 to stabilize CD24 mRNA by inhibiting STAU1-mediated mRNA decay. CD24 protects HCC cells from two indispensable mechanisms: macrophage phagocytosis and oxidative stress. Genetic knockdown or monoclonal antibody treatment of CD24 inhibits ADARp110-overexpressing tumor growth. Our findings unveil different mechanisms for ADARp110 modulation of tumor immune microenvironment and identify CD24 as a promising therapeutic target for HCCs.

Higher Intron Retention Levels in Female Alzheimer's Brains May Be Linked to Disease Prevalence.

Multimodal study of Alzheimer's disease (AD) dorsolateral prefrontal cortex (DLPFC) showed AD-related aberrant intron retention (IR) and proteomic changes not observed at the RNA level. However, the role of sex and how IR may impact the proteome are unclear. Analysis of DLPFC transcriptome showed a clear sex-biased pattern where female AD had 1645 elevated IR events compared to 80 in male AD DLPFC. Increased IR is correlated with lower mRNA levels, suggestive of nonsense-mediated mRNA decay. Two hundred thirty-three mRNAs with elevated IR in females were curated AD genes enriched for ubiquitin-like protein ligase and Tau protein binding. Increased IR genes in combined sex and female AD cohorts showed significant changes in their protein expression patterns with 11%-24% of them differential expressed proteins (DEP), alluding to the regulation of AD proteome by IR independent of RNA level. Upregulated DEPs in male AD were linked to RNA splicing that may prevent aberrant IR, whereas in female AD, they overlapped significantly more with the MAPK/metabolism module associated with cognitive decline. IR genes appeared to be significantly downregulated in specific female AD inhibitory and excitatory neurons compared to control. Differentially retained introns in female AD have elevated H3K27ac marks, strong CTCF binding at their flanking exons, and enriched for PABPC1 motif. Given that H3K27ac is repressive over gene bodies in aged brain and CTCF impedes transcription elongation, their binding patterns can delay co-transcriptional recruitment of spliceosome to cause IR, which may in turn contribute to different trajectories of AD pathology in women.

The SARS-CoV-2 nucleocapsid protein interferes with the full enzymatic activation of UPF1 and its interaction with UPF2.

The nonsense-mediated mRNA decay (NMD) pathway triggers the degradation of defective mRNAs and governs the expression of mRNAs with specific characteristics. Current understanding indicates that NMD is often significantly suppressed during viral infections to protect the viral genome. In numerous viruses, this inhibition is achieved through direct or indirect interference with the RNA helicase UPF1, thereby promoting viral replication and enhancing pathogenesis. In this study, we employed biochemical, biophysical assays and cellular investigations to explore the interplay between UPF1 and the nucleocapsid (Np) protein of SARS-CoV-2. We evaluated their direct interaction and its impact on inhibiting cellular NMD. Furthermore, we characterized how this interaction affects UPF1's enzymatic function. Our findings demonstrate that Np inhibits the unwinding activity of UPF1 by physically obstructing its access to structured nucleic acid substrates. Additionally, we showed that Np binds directly to UPF2, disrupting the formation of the UPF1/UPF2 complex essential for NMD progression. Intriguingly, our research also uncovered a surprising pro-viral role of UPF1 and an antiviral function of UPF2. These results unveil a novel, multi-faceted mechanism by which SARS-CoV-2 evades the host's defenses and manipulates cellular components. This underscores the potential therapeutic strategy of targeting Np-UPF1/UPF2 interactions to treat COVID-19.

ALKBH5, an m6A demethylase, attenuates tumor growth and inhibits metastasis in papillary thyroid carcinoma

The significance of ALKBH5 in erasing mRNA methylation in mRNA biogenesis, decay, and translation control has emerged as a prominent research focus. Additionally, ALKBH5 is associated with the development of numerous human cancers. However, it remains unclear whether ALKBH5 regulates the growth and metastasis of papillary thyroid carcinoma (PTC). Here, we compared cancer tissues and paracancerous tissues from PTC patients, along with cultured cells expressing ALKBH5 (overexpression, silent gene expression, normal stable expression). Our primary objective was to investigate the impact of ALKBH5 on PTC. Selected 30 cases of PTC tissues and their adjacent noncancerous tissues to compare the protein expression levels of ALKBH5 between the two groups using immunohistochemical analysis. qRT-PCR and western blot were used to detect the expression of ALKBH5 in normal thyroid follicular epithelial cells (Nthy-ori3-1) and 4 PTC cell lines (human PTC cell lines K1, BCPAP, IHH4, and TPC1). Appropriate cell lines were screened for subsequent experiments. Immunofluorescence staining was used to localize the high accumulation of ALKBH5 in cells. Construct the ALKBH5 knockdown vector and ALKBH5 overexpression vector separately, and construct the overexpression ALKBH5-mut vector with m6A domain mutation. The impact of different levels of ALKBH5 in the three cell lines on RNA m6A methylation levels was compared using qRT-PCR and western blot methods. Furthermore, cell viability was assessed using the CCK-8 assay, while the impact on cell proliferation was examined using plate colony formation assay. Cell invasion was evaluated using the Transwell assay. Immunohistochemical staining results showed that the expression of ALKBH5 protein in PTC cancer tissue was significantly lower than in adjacent non-cancerous tissue (P < 0.05). Lymph node metastasis in PTC patients may have been linked to ALKBH5 protein levels in their cancerous tissues (P = 0.034). The expression of ALKBH5 in PTC cell lines BCPAP, IHH4, and TPC1 was significantly lower than Nthy-ori3-1 (P < 0.05). IHH4 and TPC1 cell lines were selected for subsequent experiments. Immunofluorescence single staining results showed a high accumulation of ALKBH5 protein in the cell nucleus. Cell viability results suggested that compared to the overexpression-negative control group, cell proliferation, and invasion were significantly decreased in the ALKBH5 overexpression group (P < 0.05) and the mut-ALKBH5 overexpression group (P < 0.05). Additionally, compared to the ALKBH5 overexpression group, cell proliferation and invasion were significantly more decreased in the mut-ALKBH5 overexpression group (P < 0.05). However, compared to the interference-negative control group, cell proliferation and invasion were significantly increased in the ALKBH5 interference group (P < 0.05). The presented findings suggested that m6A demethylase ALKBH5 inhibits tumor growth and metastasis in PTC. Moreover, effective inhibition of m6A modification of ALKBH5 might constitute a potential treatment strategy for PTC.

The master male sex determinant Gdf6Y of the turquoise killifish arose through allelic neofunctionalization

Although sex determination is a fundamental process in vertebrate development, it is very plastic. Diverse genes became major sex determinants in teleost fishes. Deciphering how individual sex-determining genes orchestrate sex determination can reveal new actors in sexual development. Here, we demonstrate that the Y-chromosomal copy of the TGF-β family member gdf6 (gdf6Y) in Nothobranchius furzeri, an emerging model organism in aging research, gained the function of the male sex determinant through allelic diversification while retaining the skeletal developmental function shared with the X-chromosomal gdf6 allele (gdf6X). Concerning sex determination, gdf6Y is expressed by somatic supporting cells of the developing testes. There it induces the male sex in a germ cell-independent manner in contrast to sex determination in zebrafish and the medaka. Looking for downstream effectors of Gdf6Y, we identified besides TGF-β signaling modulators, especially the inhibitor of DNA binding genes id1/2/3, the mRNA decay activator zfp36l2 as a new GDF6 signaling target.

Divergent roles of m6A in orchestrating brown and white adipocyte transcriptomes and systemic metabolism

N6-methyladenosine (m6A) is among the most abundant mRNA modifications, yet its cell-type-specific regulatory roles remain unclear. Here we show that m6A methyltransferase-like 14 (METTL14) differentially regulates transcriptome in brown versus white adipose tissue (BAT and WAT), leading to divergent metabolic outcomes. In humans and mice with insulin resistance, METTL14 expression differs significantly from BAT and WAT in the context of its correlation with insulin sensitivity. Mettl14-knockout in BAT promotes prostaglandin secretion, improving systemic insulin sensitivity. Conversely, Mettl14-knockout in WAT triggers adipocyte apoptosis and systemic insulin resistance. m6A-seq and RNA-seq integration revealed upregulated prostaglandin biosynthesis pathways in BAT and apoptotic pathways in WAT with Mettl14 deficiency. Stable METTL14-knockout hBAs/hWAs show METTL14-mediated m6A promotes mRNA decay of PTGES2 and CBR1 in hBAs and TRAIL and TNFR1 in hWAs. These data shed light on the ability of m6A to impact metabolism in a cell-type-specific manner with implications for influencing the pathophysiology of metabolic diseases.

Nonenzymatic lysine d-lactylation induced by glyoxalase II substrate SLG dampens inflammatory immune responses

Immunometabolism is critical in the regulation of immunity and inflammation; however, the mechanism of preventing aberrant activation-induced immunopathology remains largely unclear. Here, we report that glyoxalase II (GLO2) in the glycolysis branching pathway is specifically downregulated by NF-κB signaling during innate immune activation via tristetraprolin (TTP)-mediated mRNA decay. As a result, its substrate S-D-lactoylglutathione (SLG) accumulates in the cytosol and directly induces d-lactyllysine modification of proteins. This nonenzymatic lactylation by SLG is greatly facilitated by a nearby cysteine residue, as it initially reacts with SLG to form a reversible S-lactylated thiol intermediate, followed by SN-transfer of the lactyl moiety to a proximal lysine. Lactylome profiling identifies 2255 lactylation sites mostly in cytosolic proteins of activated macrophages, and global protein structure analysis suggests that proximity to a cysteine residue determines the susceptibility of lysine to SLG-mediated d-lactylation. Furthermore, lactylation is preferentially enriched in proteins involved in immune activation and inflammatory pathways, and d-lactylation at lysine 310 (K310) of RelA attenuates inflammatory signaling and NF-κB transcriptional activity to restore immune homeostasis. Accordingly, TTP-binding site mutation or overexpression of GLO2 in vivo blocks this feedback lactylation in innate immune cells and promotes inflammation, whereas genetic deficiency or pharmacological inhibition of GLO2 restricts immune activation and attenuates inflammatory immunopathology both in vitro and in vivo. Importantly, dysregulation of the GLO2/SLG/d-lactylation regulatory axis is closely associated with human inflammatory phenotypes. Overall, our findings uncover an immunometabolic feedback loop of SLG-induced nonenzymatic d-lactylation and implicate GLO2 as a promising target for combating clinical inflammatory disorders.

A new hypothesis to explain disease dominance.

The onset and progression of dominant diseases are thought to result from haploinsufficiency or dominant negative effects. Here, we propose transcriptional adaptation (TA), a newly identified response to mRNA decay, as an additional cause of some dominant diseases. TA modulates the expression of so-called adapting genes, likely via mRNA decay products, resulting in genetic compensation or a worsening of the phenotype. Recent studies have challenged the current concepts of haploinsufficiency or poison proteins as the mechanisms underlying certain dominant diseases, including Brugada syndrome, hypertrophic cardiomyopathy, and frontotemporal lobar degeneration. We hypothesize that for these and other dominant diseases, when the underlying mutation leads to mRNA decay, the phenotype is due at least partly to the dysregulation of gene expression via TA.

Proper 5'-3' cotranslational mRNA decay in yeast requires import of Xrn1 to the nucleus.

The budding yeast Xrn1 protein shuttles between the nucleus, where it stimulates transcription, and the cytoplasm, where it executes the major cytoplasmic mRNA decay. In the cytoplasm, apart from catalyzing 5'→3' decay onto non translated mRNAs, Xrn1 can follow the last translating ribosome to degrade the decapped mRNA template, a process known as "cotranslational mRNA decay". We have previously observed that the import of Xrn1 to the nucleus is required for efficient cytoplasmic mRNA decay. Here by using an Xrn1 mutant that cannot enter the nucleus, but is otherwise functional in ribonuclease activity, we show that nuclear import is necessary for proper global cotranslational decay of mRNAs along coding regions and also affects degradation in the of 5' region of a large group of mRNAs, which comprise about 20% of the transcriptome. Furthermore, a principal component analysis of the genomic datasets of this mutant and other Xrn1 mutants also shows that lack of a cytoplasmic 5'→3' exoribonuclease is the primary cause of the physiological defects seen in a xrn1Δ mutant, but also suggests that Xrn1 import into the nucleus is necessary for its full in vivo functions.

YTHDF2 promotes arsenic-induced malignant phenotypes by degrading PIDD1 mRNA in human keratinocytes.

Arsenic is a widespread environmental carcinogen, and its carcinogenic mechanism has been the focus of toxicology. N6-methyladenosine (m6A) binding protein YTH domain family protein 2 (YTHDF2) performs various biological functions by degrading m6A-modified mRNAs. However, the m6A-modified target mRNA of YTHDF2 in regulating arsenic carcinogenesis remains largely unknown. To explore the effect of YTHDF2 in regulating arsenic carcinogenicity, we exposed the human keratinocyte HaCaT cells to 1μM sodium arsenite for 50 generations to create a cell model of arsenic carcinogenesis (HaCaT-T). Our results demonstrated that YTHDF2 protein levels were higher in HaCaT-T cells than HaCaT cells, and knockdown of YTHDF2 significantly inhibited arsenic-induced malignant phenotypes. In addition, m6A levels in HaCaT-T cells were remarkably elevated, accompanied by abnormal expression of m6A methyltransferases and m6A demethylases. Mechanistically, YTHDF2 bound to p53-induced death domain protein 1 (PIDD1) mRNA in an m6A-dependent manner, thereby promoting the degradation of PIDD1 mRNA. Moreover, the decay of PIDD1 mRNA inhibited the formation of PIDDosome complex that is essential for activating the apoptosis initiator caspase-2, leading to a decrease in caspase-2-dependent mitochondrial apoptosis and subsequently promoting the malignant phenotypes of HaCaT-T cells. Collectively, our study reveals the role of YTHDF2 in arsenic-induced malignant phenotypes of human keratinocytes through direct interaction with PIDD1 mRNA in an m6A-dependent manner, which provides new insight into the precise mechanism underlying arsenic-induced skin cancer.

A Novel Heterozygous and Pathogenic Variant of the HNF1B Gene Associated with Autosomal Dominant Tubulointerstitial Kidney Disease with a Broad Spectrum of Extrarenal Phenotypes: A Case Report.

We encountered a family with hereditary renal failure, renal medullary cysts, pancreatic hypoplasia, hypomagnesemia, liver enzyme abnormalities, and diabetes mellitus (DM). We identified a novel heterozygous variant of HNF1B (NM_000458.4:c.791dup, p.L264Ffs*30) using whole-exome sequencing of genomic DNA samples from this family. This variant is located in the DNA-binding domain of the HNF1B protein and produces a truncated protein with a de novo sequence, suggesting that this variant changes HNF1B binding to genomic DNA or causes nonsense-mediated mRNA decay. Based on the phenotypes and identified gene variants, this family suffers from autosomal dominant tubulointerstitial kidney disease caused by this HNF1B variant.

Acute heat stress regulates estradiol synthesis in ovine ovarian granulosa cells through the SREBPs/MVK–LHR pathway

The adverse effects of heat stress on reproductive performance of sheep are becoming increasingly severe. Previous research has revealed that heat stress decreases both cholesterol and estradiol content; however, regulation of estradiol by cholesterol and its regulatory mechanism under heat stress are unclear. Mevalonate kinase (MVK), a key cholesterol synthesis pathway enzyme, binds to the luteinizing hormone receptor (LHR; a key gene regulating hormone synthesis) mRNA. In this study, ovine ovarian granulosa cells (GCs) were used in an in vitro model. To elucidate the underlying molecular mechanism, immunofluorescence, quantitative reverse transcription polymerase chain reaction, western blotting, enzyme-linked immunosorbent assay, and an RNA electrophoretic mobility shift assay (REMSA) were used to investigate whether the decrease in cholesterol caused by acute heat stress resulted in a decrease in estradiol synthesis. Acute heat stress reduced the cholesterol content in ovine ovarian GCs, which transactivated the cholesterol synthesis pathway corresponding to the gene expression of sterol regulatory element-binding protein (SREBP-1A), SREBP-2, and MVK. Upregulated MVK increased the MVK–LHR mRNA complex, which caused LHR mRNA decay and downregulation, further leading to the downregulation of CYP19A1 and a decrease in estradiol. The cholesterol synthesis inhibitor, PF-429242, alleviated the decrease in estradiol synthesis caused by acute heat stress. Overall, acute heat stress caused a decrease in total cholesterol, which transactivated the expression of cholesterol synthesis genes, such as SREBP-1A, SREBP2, and MVK, increasing the MVK–LHR complex, downregulating LHR expression, and further decreasing estradiol.

Human eRT1 Translation Regulation

Translation termination factor eRF1 is an important cellular protein that plays a key role in translation termination, nonsense-mediated mRNA decay (NMD), and stop-codons readthrough. An amount of eRF1 in the cell influences all these processes. The mechanism of eRF1 translation regulation through an autoregulatory NMD-dependent expression circuit has been described for plants and fungi, but the mechanisms of human eRF1 translation regulation have not yet been studied. Using reporter constructs, we studied the effect of eRF1 mRNA elements on its translation in cell-free translation systems and HEK293 cells. Our data do not support the presence of the NMD-dependent autoregulatory circuit of human eRF1 expression. We found that the 5'-untranslated region (5'-UTR) of eRF1 mRNA and the start codon of the upstream open reading frame (uORF) have the greatest influence on the translation of CDS. According to the DataBase of Transcriptional Start Sites (DBTSS), eRF1 mRNA has a high heterogeneity of transcription start sites and variable length of 5'-UTRs as a consequence. Moreover, the start codon of the eRF1 CDS is located within the known Translation Initiator of Short 5′UTR (TISU), which also stimulates mRNA transcription of genes with high transcription start heterogeneity. We hypothesize that regulation of eRF1 mRNA translation occurs at both the transcriptional and translational levels. At the transcription level, the length of the 5'-UTRs of eRF1 and the number of short open reading frames in it are regulated, which in turn regulate eRF1 production at the translational level.