microRNA Biogenesis Research Articles

MicroRNA Biogenesis during Cellular Senesence Induced by Chronic Stress of the Endoplasmic Reticulum

MicroRNAs are small non-coding regulatory RNAs about 22 nt long, post-transcriptional and transcriptional regulators of gene expression that stabilize the cellular phenotype and play an important role in differentiation, development, and apoptosis. MicroRNA biogenesis includes several precisely controlled post-transcriptional stages of processing and transport, including cytoplasmic cleavage of pre-miRNA by type III ribonuclease DICER with the formation of a mature duplex included in the RISC complex. The role of miRNA and its biogenesis are not well understood in such an important process as cellular stress. Cellular stress is a non-specific cellular response to non-physiological stimuli that can switch a cell to death or cellular senescence. The global decrease in microRNA levels is a key feature of cancer cells and an important reason for the formation of a malignant phenotype. In this work, using flow cytometry and high-throughput analysis of gene expression, we showed that chronic endoplasmic reticulum (ER) stress, one of the types of cellular stress associated with impaired protein folding in the ER, leads to the formation of a cellular aging phenotype in fibroblast-like FRSN cells. Despite the fact that acute ER stress can reduce miRNA biogenesis, chronic stress does not lead to a significant drop in global miRNA expression and is accompanied by only a slight decrease in DICER1 mRNA expression. Under chronic ER stress, we found an increase in cell population heterogeneity in terms of lysosomal beta-galactosidase activity, which does not exclude induced or initial cell heterogeneity and in terms of expression of microRNA biogenesis pathway components.

Five-minute exposure to a novel appetitive food substance is sufficient time for a microRNA-dependent long-term memory to form.

The Garcia effect is a unique form of conditioned taste aversion which requires that a novel food stimulus be followed sometime later by a sickness state associated with the novel food stimulus. The long-lasting associative memory resulting from the Garcia effect ensures that organisms avoid toxic foods in their environment. Considering its ecological relevance, we sought to investigate whether a brief encounter (5min) with a novel, appetitive food stimulus can cause a persisting long-term memory (LTM) to form that would in turn block the Garcia effect in Lymnaea stagnalis. Furthermore, we wanted to explore whether that persisting LTM could be modified by the alteration of microRNAs via an injection of poly-L-lysine (PLL), an inhibitor of Dicer-mediated microRNA biogenesis. The Garcia effect procedure involved two observations of feeding behavior in carrot separated by a heat stress (30°C for 1h). Exposing snails to carrot for 5min caused a LTM to form and persist for 1week, effectively preventing the Garcia effect in snails. In contrast, PLL injection following the 5-min carrot exposure impaired LTM formation, allowing the Garcia effect to occur. These results provide more insight into LTM formation and the Garcia effect, an important survival mechanism.

Altered MicroRNA Maturation in Ischemic Hearts: Implication of Hypoxia on XPO5 and DICER1 Dysregulation and RedoximiR State.

Ischemic cardiomyopathy (ICM) is associated with abnormal microRNA expression levels that involve an altered gene expression profile. However, little is known about the underlying causes of microRNA disruption in ICM and whether microRNA maturation is compromised. Therefore, we focused on microRNA maturation defects analysis and the implication of the microRNA biogenesis pathway and redox-sensitive microRNAs (redoximiRs). Transcriptomic changes were investigated via ncRNA-seq (ICM, n = 22; controls, n = 8) and mRNA-seq (ICM, n = 13; control, n = 10). The effect of hypoxia on the biogenesis of microRNAs was evaluated in the AC16 cell line. ICM patients showed a reduction in microRNA maturation compared to control (4.30 ± 0.94 au vs. 5.34 ± 1.07 au, p ˂ 0.05), accompanied by a deregulation of the microRNA biogenesis pathway: a decrease in pre-microRNA export (XPO5, FC = -1.38, p ˂ 0.05) and cytoplasmic processing (DICER, FC = -1.32, p ˂ 0.01). Both processes were regulated by hypoxia in AC16 cells (XPO5, FC = -1.65; DICER1, FC = -1.55; p ˂ 0.01; Exportin-5, FC = -1.81; Dicer, FC = -1.15; p ˂ 0.05). Patients displayed deregulation of several redoximiRs, highlighting miR-122-5p (FC = -2.41, p ˂ 0.001), which maintained a good correlation with the ejection fraction (r = 0.681, p ˂ 0.01). We evidenced a decrease in microRNA maturation mainly linked to a decrease in XPO5-mediated pre-microRNA export and DICER1-mediated processing, together with a general effect of hypoxia through deregulation of biogenesis pathway and the redoximiRs.

LIN28B and Let-7 in Diffuse Midline Glioma: A Review

Diffuse midline glioma (DMG) is the most lethal of all childhood cancers. DMGs are driven by histone-tail-mutation-mediated epigenetic dysregulation and partner mutations in genes controlling proliferation and migration. One result of this epigenetic and genetic landscape is the overexpression of LIN28B RNA binding protein. In other systems, LIN28B has been shown to prevent let-7 microRNA biogenesis; however, let-7, when available, faithfully suppresses tumorigenic pathways and induces cellular maturation by preventing the translation of numerous oncogenes. Here, we review the current literature on LIN28A/B and the let-7 family and describe their role in gliomagenesis. Future research is then recommended, with a focus on the mechanisms of LIN28B overexpression and localization in DMG.

SRSF3 shapes the structure of miR‐17‐92 cluster RNA and promotes selective processing of miR‐17 and miR‐20a

MicroRNA (miRNA) biogenesis is tightly regulated to maintain distinct miRNA expression patterns. Almost half of mammalian miRNAs are generated from miRNA clusters, but this process is not well understood. We show here that Serine‐arginine rich splicing factor 3 (SRSF3) controls the processing of miR‐17‐92 cluster miRNAs in pluripotent and cancer cells. SRSF3 binding to multiple CNNC motifs downstream of Drosha cleavage sites within miR‐17‐92 is required for the efficient processing of the cluster. SRSF3 depletion specifically compromises the processing of two paralog miRNAs, miR‐17 and miR‐20a. In addition to SRSF3 binding to the CNNC sites, the SRSF3 RS‐domain is essential for miR‐17‐92 processing. SHAPE‐MaP probing demonstrates that SRSF3 binding disrupts local and distant base pairing, resulting in global changes in miR‐17‐92 RNA structure. Our data suggest a model where SRSF3 binding, and potentially its RS‐domain interactions, may facilitate an RNA structure that promotes miR‐17‐92 processing. SRSF3‐mediated increase in miR‐17/20a levels inhibits the cell cycle inhibitor p21, promoting self‐renewal in normal and cancer cells. The SRSF3‐miR‐17‐92‐p21 pathway operates in colorectal cancer, linking SRSF3‐mediated pri‐miRNA processing and cancer pathogenesis.

DICER1 platform domain missense variants inhibit miRNA biogenesis and lead to tumor susceptibility.

The endoribonuclease DICER1 plays an essential role in the microRNA (miRNA) biogenesis pathway, cleaving precursor miRNA (pre-miRNA) stem-loops to generate mature single-stranded miRNAs. Germline pathogenic variants (GPVs) in DICER1 result in DICER1 tumor predisposition syndrome (DTPS), a mainly childhood-onset tumor susceptibility disorder. Most DTPS-causing GPVs are nonsense or frameshifting, with tumor development requiring a second somatic missense hit that impairs the DICER1 RNase IIIb domain. Interestingly, germline DICER1 missense variants that cluster in the DICER1 Platform domain have been identified in some persons affected by tumors that also associate with DTPS. Here, we demonstrate that four of these Platform domain variants prevent DICER1 from producing mature miRNAs and as a result impair miRNA-mediated gene silencing. Importantly, we show that in contrast to canonical somatic missense variants that alter DICER1 cleavage activity, DICER1 proteins harboring these Platform variants fail to bind to pre-miRNA stem-loops. Taken together, this work sheds light upon a unique subset of GPVs causing DTPS and provides new insights into how alterations in the DICER1 Platform domain can impact miRNA biogenesis.

A Glance at Biogenesis and Functionality of MicroRNAs and Their Role in the Neuropathogenesis of Parkinson's Disease.

MicroRNAs (miRNAs) are short, noncoding RNA transcripts. Mammalian miRNA coding sequences are located in introns and exons of genes encoding various proteins. As the central nervous system is the largest source of miRNA transcripts in living organisms, miRNA molecules are an integral part of the regulation of epigenetic activity in physiological and pathological processes. Their activity depends on many proteins that act as processors, transporters, and chaperones. Many variants of Parkinson's disease have been directly linked to specific gene mutations which in pathological conditions are cumulated resulting in the progression of neurogenerative changes. These mutations can often coexist with specific miRNA dysregulation. Dysregulation of different extracellular miRNAs has been confirmed in many studies on the PD patients. It seems reasonable to conduct further research on the role of miRNAs in the pathogenesis of Parkinson's disease and their potential use in future therapies and diagnosis of the disease. This review presents the current state of knowledge about the biogenesis and functionality of miRNAs in the human genome and their role in the neuropathogenesis of Parkinson's disease (PD)-one of the most common neurodegenerative disorders. The article also describes the process of miRNA formation which can occur in two ways-the canonical and noncanonical one. However, the main focus was on miRNA's use in in vitro and in vivo studies in the context of pathophysiology, diagnosis, and treatment of PD. Some issues, especially those regarding the usefulness of miRNAs in PD's diagnostics and especially its treatment, require further research. More standardization efforts and clinical trials on miRNAs are needed.

The Cajal body marker protein coilin is SUMOylated and possesses SUMO E3 ligase-like activity

Cajal bodies (CBs) are subnuclear domains that contribute to the biogenesis of several different classes of ribonucleoproteins (RNPs), including small nuclear RNPs. Only some cell types contain abundant CBs, such as neuronal cells and skeletal muscle, but CBs are invariant features of transformed cells. In contrast, coilin, the CB marker protein, is a ubiquitously expressed nuclear protein, but the function of coilin in cell types that lack CBs is not well understood. We have previously shown that coilin promotes microRNA biogenesis by promoting phosphorylation of DGCR8, a component of the microprocessor. Here, we identify seven additional residues of DGCR8 with decreased phosphorylation upon coilin knockdown. In addition to phosphorylation, the addition of a small ubiquitin-like modifier (SUMO) to DGCR8 also increases its stability. Because of coilin’s role in the promotion of DGCR8 phosphorylation, we investigated whether coilin is involved in DGCR8 SUMOylation. We show that coilin knockdown results in global decrease of protein SUMOylation, including decreased DGCR8 and Sp100 (a PML body client protein) SUMOylation and decreased SMN expression. Alternatively, we found that coilin expression rescued Sp100 SUMOylation and increased DGCR8 and SMN levels in a coilin knockout cell line. Furthermore, we found that coilin facilitates RanGAP1 SUMOylation, interacts directly with components of the SUMOylation machinery (Ubc9 and SUMO2), and, itself, is SUMOylated in vitro and in vivo. In summary, we have identified coilin as a regulator of DGCR8 phosphorylation and a promotor of protein SUMOylation with SUMO E3 ligase-like activity.

The role of miRNAs in laryngeal cancer pathogenesis and therapeutic resistance - A focus on signaling pathways interplay.

Laryngeal cancer (LC)is the malignancy of the larynx (voice box). The majority of LC are squamous cell carcinomas. Many risk factors were reported to be associated with LC as tobacco use, obesity, alcohol intake, human papillomavirus (HPV) infection, and asbestos exposure. Besides, epigenetics as non-coding nucleic acids also have a great role in LC. miRNAs are short nucleic acid molecules that can modulate multiple cellular processes by regulating the expression of their genes. Therefore, LC progression, apoptosis evasions, initiation, EMT, and angiogenesis are associated with dysregulated miRNA expressions. miRNAs also could have some vital signaling pathways such as mTOR/P-gp, Wnt/-catenin signaling, JAK/STAT, KRAS, and EGF. Besides, miRNAs also have a role in the modulation of LC response to different therapeutic modalities. In this review, we have provided a comprehensive and updated overview highlighting the microRNAs biogenesis, general biological functions, regulatory mechanisms, and signaling dysfunction in LC carcinogenesis, in addition to their clinical potential for LC diagnosis, prognosis, and chemotherapeutics response implications.

MiR-147 Represses NDUFA4, Inducing Mitochondrial Dysfunction and Tubular Damage in Cold Storage Kidney Transplantation.

Cold storage-associated transplantation (CST) injury occurs in renal transplant from deceased donors, the main organ source. The pathogenesis of CST injury remains poorly understood, and effective therapies are not available. This study has demonstrated an important role of microRNAs in CST injury and revealed the changes in microRNA expression profiles. Specifically, microRNA-147 (miR-147) is consistently elevated during CST injury in mice and in dysfunctional renal grafts in humans. Mechanistically, NDUFA4 (a key component of mitochondrial respiration complex) is identified as a direct target of miR-147. By repressing NDUFA4, miR-147 induces mitochondrial damage and renal tubular cell death. Blockade of miR-147 and overexpression of NDUFA4 reduce CST injury and improve graft function, unveiling miR-147 and NDUFA4 as new therapeutic targets in kidney transplantation. Kidney injury due to cold storage-associated transplantation (CST) is a major factor determining the outcome of renal transplant, for which the role and regulation of microRNAs remain largely unclear. The kidneys of proximal tubule Dicer (an enzyme for microRNA biogenesis) knockout mice and their wild-type littermates were subjected to CST to determine the function of microRNAs. Small RNA sequencing then profiled microRNA expression in mouse kidneys after CST. Anti-microRNA-147 (miR-147) and miR-147 mimic were used to examine the role of miR-147 in CST injury in mouse and renal tubular cell models. Knockout of Dicer from proximal tubules attenuated CST kidney injury in mice. RNA sequencing identified multiple microRNAs with differential expression in CST kidneys, among which miR-147 was induced consistently in mouse kidney transplants and in dysfunctional human kidney grafts. Anti-miR-147 protected against CST injury in mice and ameliorated mitochondrial dysfunction after ATP depletion injury in renal tubular cells in intro . Mechanistically, miR-147 was shown to target NDUFA4, a key component of the mitochondrial respiration complex. Silencing NDUFA4 aggravated renal tubular cell death, whereas overexpression of NDUFA4 prevented miR-147-induced cell death and mitochondrial dysfunction. Moreover, overexpression of NDUFA4 alleviated CST injury in mice. microRNAs, as a class of molecules, are pathogenic in CST injury and graft dysfunction. Specifically, miR-147 induced during CST represses NDUFA4, leading to mitochondrial damage and renal tubular cell death. These results unveil miR-147 and NDUFA4 as new therapeutic targets in kidney transplantation.

The HOS15-HDA9 complex associates with HYL1 to modulate miRNA expression in response to ABA signaling.

The regulation of microRNA (miRNA) biogenesis is crucial for maintaining plant homeostasis under biotic and abiotic stress. The crosstalk between the RNA polymerase II (Pol-II) complex and the miRNA processing machinery has emerged as a central hub modulating transcription and co-transcriptional processing of primary miRNA transcripts (pri-miRNAs). However, it remains unclear how miRNA-specific transcriptional regulators recognize MIRNA loci. Here, we show that the Arabidopsis (Arabidopsis thaliana) HIGH EXPRESSION OF OSMOTICALLY RESPONSIVE GENE15 (HOS15)-HISTONE DEACETYLASE9 (HDA9) complex is a conditional suppressor of miRNA biogenesis, particularly in response to ABA. When treated with ABA, hos15/hda9 mutants show enhanced transcription of pri-miRNAs that is accompanied by increased processing, leading to over-accumulation of a set of mature miRNAs. Moreover, upon recognition of the nascent pri-miRNAs, the ABA-induced recruitment of the HOS15-HDA9 complex to MIRNA loci is guided by HYPONASTIC LEAVES 1 (HYL1). The HYL1-dependent recruitment of the HOS15-HDA9 complex to MIRNA loci suppresses expression of MIRNAs and processing of pri-miRNA. Most importantly, our findings indicate that nascent pri-miRNAs serve as scaffolds for recruiting transcriptional regulators, specifically to MIRNA loci. This indicates that RNA molecules can act as regulators of their own expression by causing a negative feedback loop that turns off their transcription, providing a self-buffering system.

Abscisic acid-regulated microRNA biogenesis through HYPONASTIC LEAVES1.

Abscisic acid-regulated microRNA biogenesis through HYPONASTIC LEAVES1.

Solution structure and behaviour of the Arabidopsis thaliana HYL1 protein

In plants, microRNA biogenesis involves the complex assembly of molecular processes that are mostly governed by three proteins: RNase III protein DCL1 and two RNA binding proteins, SERRATE and HYL1. HYL1 protein is a double stranded RNA binding protein that is needed for the precise excision of miRNA/miRNA* duplex from the stem-loop containing primary miRNA gene transcripts. Moreover, HYL1 protein partners with HSP90 and CARP9 proteins to load the miRNA molecules onto the AGO1 endonuclease. HYL1 protein as a crucial player in the biogenesis pathway is regulated by its phosphorylation status to fine tune the levels of miRNA in various physiological conditions. HYL1 protein consists of two dsRNA binding domains (dsRBD) that are involved in RNA binding and dimerization and a C-terminal disordered tail of unknown function. Although the spatial structures of the individual dsRBDs have been determined there is a lack of information about the behaviour and structure of the full length protein. Using small the angle X-ray scattering (SAXS) technique we investigated the structure and dynamic of the HYL1 protein from Arabidopsis thaliana in solution. We show that the C-terminal domain is disordered and dynamic in solution and that HYL1 protein dimerization is dependent on the concentration. HYL1 protein lacking a C-terminal tail and a nuclear localisation signal (NLS) fragment is almost exclusively monomeric and similarly to full-length protein has a dynamic nature in solution. Our results point for the first time to the role of the C-terminal fragment in stabilisation of HYL1 dimer formation.

MicroRNA-216a is essential for cardiac angiogenesis

While it is experimentally supported that impaired myocardial vascularization contributes to a mismatch between myocardial oxygen demand and supply, a mechanistic basis for disruption of coordinated tissue growth and angiogenesis in heart failure remains poorly understood. Silencing strategies that impair microRNA biogenesis have firmly implicated microRNAs in the regulation of angiogenesis, and individual microRNAs prove to be crucial in developmental or tumor angiogenesis. A high-throughput functional screening for the analysis of a whole-genome microRNA silencing library with regard to their phenotypic effect on endothelial cell proliferation as a key parameter, revealed several anti- and pro-proliferative microRNAs. Among those was miR-216a, a pro-angiogenic microRNA which is enriched in cardiac microvascular endothelial cells and reduced in expression under cardiac stress conditions. miR-216a null mice display dramatic cardiac phenotypes related to impaired myocardial vascularization and unbalanced autophagy and inflammation, supporting a model where microRNA regulation of microvascularization impacts the cardiac response to stress.

Abstract 23: Development of a biallelicDicer1mutant mouse strain for studying the pathogenesis of DICER1 syndrome-associated cancer

Abstract DICER1 encodes a RNase III enzyme that post-transcriptionally controls gene expression through governing microRNA (miRNA) biogenesis. We and others have demonstrated that somatic mutations of DICER1 at its RNase IIIb domain metal binding sites, impairing its capability to produce mature miRNAs from the 5P strand of miRNA precursors, occur recurrently in a broad spectrum of cancers associated with the DICER1 syndrome that affects children and youths predominantly. The biallelic DICER1 mutations in these cancers challenge the two-hit hypothesis theory of traditional tumour suppressors, but it remains unproven whether these mutations are sufficient to drive tumorigenesis. The lack of biology relevant preclinical models has also hindered the understanding the pathogenesis. Here, we developed a genetically engineered mouse strain that expresses an inducible knockin Dicer1 missense mutation (Dicer1+/fl-D1693N), equivalent to the DICER1 RNase IIIb hotspot mutation D1709N in human cancers. This conditional strain behaves as a null allele due to an aberrant splicing event without Cre-mediated recombination. When crossed with a well-characterized conditional null Dicer1 strain (Dicer1fl/fl), the resulting compound heterozygous strain (Dicer1fl/fl-D1693N), acts as a hemizygous wildtype allele that is converted to a hemizygous missense mutation allele upon Cre-mediated recombination, reflecting the genetic status of DICER1 in DICER1 syndrome-associated cancer. When crossing with the anti-Mullerian hormone receptor 2 (Amhr2) driven cre strain (Amhr2+/cre), the biallelic Dicer1 mutation resulted in infertility in females by impairing the development of oviduct and endometrium and ultimately drove the development of multicystic tubal and intra-uterine tumours. Histologically, these murine tumors resemble human Müllerian adenosarcoma and other DICER1 syndrome-associated sarcomas. Molecular analysis of these murine tumours validated the miRNA biogenesis defects in 5P-miRNA production, uncovered the activation of the myc signaling and identified that loss of let-7 family miRNAs may drive the transcriptomic rewiring and malignant transformation. Thus, this first DICER1 syndrome-associated murine cancer model faithfully recapitulates the biology of human cancer and provides a unique tool for future investigation and therapeutic development. Citation Format: Yemin Wang, Shary Chen, Janine Senz, Maxwell Douglas, Shelby Thornton, Yana Moscovitz, C. Blake Gilks, David Huntsman, Gregg Morin. Development of a biallelicDicer1mutant mouse strain for studying the pathogenesis of DICER1 syndrome-associated cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 23.

A case–control study of single-nucleotide variants in microRNA biogenesis genes (AGO1 and GEMIN4) in people with primary immune thrombocytopenia

BackgroundThe role of microRNA (miRNA) is to regulate the translation of genes involved in a variety of diseases.Aim of the workThis study investigated the relation between the rs636832 and rs2740348 single-nucleotide polymorphisms (SNPs) of the AGO1 gene and the GEMIN4 gene of miRNA biogenesis genes and the risk for primary ITP and the response to therapy.Patients and methodsIn this case–control study, 100 patients with immune thrombocytopenic purpura from the clinical hematology department and outpatient clinic were compared to 100 control subjects. Patients' blood samples are taken, and DNA extraction and PCR amplification of rs636832 A/G of AGO1 and rs2740348 G/C of GEMIN4 were done on sera and compared to the clinical status of the patients.ResultsAccording to statistical analysis, the genotype and allele frequencies of both variants did not differ significantly between cases and controls. The GG genotype was found to be more prevalent in the chronic phase of ITP than the AA and AG genotypes, with a significance level of p 0.05. The GG genotype was found to be more prevalent in the chronic phase of ITP than the AA and AG genotypes, with a significance level of p 0.05. In addition, the GG genotype was more prevalent in ITP patients who did not respond to treatment compared to the AA and AG genotypes, although this difference was not statistically significant. Concerning rs2740348: the CC genotype was more common than the GC genotype in ITP cases that did not respond to treatment and needed a second line of therapy like splenectomy or TPO-RA, but this did not reach statistical significance.ConclusionThe rs636832 and rs2740348 SNPs did not appear to be risk factors for ITP; however, the rs636832:GG genotype was more prevalent in older patients, who tend to have the chronic phase of the disease. Although this distinction was not statistically significant, they were less responsive to therapy than the AA and AG genotypes. Concerning rs2740348: the CC genotype was more common than the GC genotype in ITP cases that did not respond to treatment and needed a second line of therapy like splenectomy or TPO-RA, but this did not reach statistical significance.

The Transcription Factor NRF2 Has Epigenetic Regulatory Functions Modulating HDACs, DNMTs, and miRNA Biogenesis.

The epigenetic regulation of gene expression is a complex and tightly regulated process that defines cellular identity and is associated with health and disease processes. Oxidative stress is capable of inducing epigenetic modifications. The transcription factor NRF2 (nuclear factor erythroid-derived 2-like 2) is a master regulator of cellular homeostasis, regulating genes bearing antioxidant response elements (AREs) in their promoters. Here, we report the identification of ARE sequences in the promoter regions of genes encoding several epigenetic regulatory factors, such as histone deacetylases (HDACs), DNA methyltransferases (DNMTs), and proteins involved in microRNA biogenesis. In this research, we study this possibility by integrating bioinformatic, genetic, pharmacological, and molecular approaches. We found ARE sequences in the promoter regions of genes encoding several HDACs, DNMTs, and proteins involved in miRNA biogenesis. We confirmed that NRF2 regulates the production of these genes by studying NRF2-deficient cells and cells treated with dimethyl fumarate (DMF), an inducer of the NRF2 signaling pathway. In addition, we found that NRF2 could be involved in the target RNA-dependent microRNA degradation (TDMD) of miR-155-5p through its interaction with Nfe2l2 mRNA. Our data indicate that NRF2 has an epigenetic regulatory function, complementing its traditional function and expanding the regulatory dimensions that should be considered when developing NRF2-centered therapeutic strategies.

An antisense intragenic lncRNA SEAIRa mediates transcriptional and epigenetic repression of SERRATE in Arabidopsis

SERRATE (SE) is a core protein for microRNA (miRNA) biogenesis as well as for mRNA alternative splicing. Investigating the regulatory mechanism of SE expression is hence critical to understanding its detailed function in diverse biological processes. However, little about the control of SE expression has been clarified, especially through long noncoding RNA (lncRNA). Here, we identified an antisense intragenic lncRNA transcribed from the 3' end of SE, named SEAIRa. SEAIRa repressed SE expression, which in turn led to serrated leaves. SEAIRa recruited plant U-box proteins PUB25/26 with unreported RNA binding ability and a ubiquitin-like protein related to ubiquitin 1 (RUB1) for H2A monoubiquitination (H2Aub) at exon 11 of SE. In addition, PUB25/26 helped cleave SEAIRa and release the 5' domain fragment, which recruited the PRC2 complex for H3 lysine 27 trimethylation (H3K27me3) deposition at the first exon of SE. The distinct modifications of H2Aub and H3K27me3 at different sites of the SE locus cooperatively suppressed SE expression. Collectively, our results uncover an epigenetic mechanism mediated by the lncRNA SEAIRa that modulates SE expression, which is indispensable for plant growth and development.

The roles of microRNAs in horticultural plant disease resistance.

The development of the horticultural industry is largely limited by disease and excessive pesticide application. MicroRNAs constitute a major portion of the transcriptomes of eukaryotes. Various microRNAs have been recognized as important regulators of the expression of genes involved in essential biological processes throughout the whole life cycle of plants. Recently, small RNA sequencing has been applied to study gene regulation in horticultural plants. In this review, we summarize the current understanding of the biogenesis and contributions of microRNAs in horticultural plant disease resistance. These microRNAs may potentially be used as genetic resources for improving disease resistance and for molecular breeding. The challenges in understanding horticultural plant microRNA biology and the possibilities to make better use of these horticultural plant gene resources in the future are discussed in this review.

Regulation of SUMOylation on RNA metabolism in cancers.

Post-translational modifications of proteins play very important roles in regulating RNA metabolism and affect many biological pathways. Here we mainly summarize the crucial functions of small ubiquitin-like modifier (SUMO) modification in RNA metabolism including transcription, splicing, tailing, stability and modification, as well as its impact on the biogenesis and function of microRNA (miRNA) in particular. This review also highlights the current knowledge about SUMOylation regulation in RNA metabolism involved in many cellular processes such as cell proliferation and apoptosis, which is closely related to tumorigenesis and cancer progression.