Choroid plexus mast cells drive tumor-associated hydrocephalus.

Tumor-associated hydrocephalus (TAH) is a common and lethal complication of brain metastases. Although other factors beyond mechanical obstructions have been suggested, the exact mechanisms are unknown. Using single-nucleus RNA sequencing and spatial transcriptomics, we find that a distinct population of mast cells locate in the choroid plexus and dramatically increase during TAH. Genetic fate tracing and intracranial mast-cell-specific tryptase knockout showed that choroid plexus mast cells (CPMCs) disrupt cilia of choroid plexus epithelia via the tryptase-PAR2-FoxJ1 pathway and consequently increase cerebrospinal fluid production. Mast cells are also found in the human choroid plexus. Levels of tryptase in cerebrospinal fluid are closely associated with clinical severity of TAH. BMS-262084, an inhibitor of tryptase, can cross the blood-brain barrier, inhibit TAH in vivo, and alleviate mast-cell-induced damage of epithelial cilia in a human pluripotent stem-cell-derived choroid plexus organoid model. Collectively, we uncover the function of CPMCs and provide an attractive therapy for TAH.

Targeting Mitochondria-Located circRNA SCAR Alleviates NASH via Reducing mROS Output.

Mitochondria, which play central roles in immunometabolic diseases, have their own genome. However, the functions of mitochondria-located noncoding RNAs are largely unknown due to the absence of a specific delivery system. By circular RNA (circRNA) expression profile analysis of liver fibroblasts from patients with nonalcoholic steatohepatitis (NASH), we observe that mitochondrial circRNAs account for a considerable fraction of downregulated circRNAs in NASH fibroblasts. By constructing mitochondria-targeting nanoparticles, we observe that Steatohepatitis-associated circRNA ATP5B Regulator (SCAR), which is located in mitochondria, inhibits mitochondrial ROS (mROS) output and fibroblast activation. circRNA SCAR, mediated by PGC-1α, binds to ATP5B and shuts down mPTP by blocking CypD-mPTP interaction. Lipid overload inhibits PGC-1α by endoplasmic reticulum (ER) stress-induced CHOP. In vivo, targeting circRNA SCAR alleviates high fat diet-induced cirrhosis and insulin resistance. Clinically, circRNA SCAR is associated with steatosis-to-NASH progression. Collectively, we identify a mitochondrial circRNA that drives metaflammation and serves as a therapeutic target for NASH.

Complement Signals Determine Opposite Effects of B Cells in Chemotherapy-Induced Immunity.

Understanding molecular mechanisms that dictate B cell diversity is important for targeting B cells as anti-cancer treatment. Through the single-cell dissection of B cell heterogeneity in longitudinal samples of patients with breast cancer before and after neoadjuvant chemotherapy, we revealed that an ICOSL+ B cell subset emerges after chemotherapy. Using three immunocompetent mouse models, we recapitulated the subset switch of human tumor-infiltrating B cells during chemotherapy. By employing B-cell-specific deletion mice, we showed that ICOSL in B cells boosts anti-tumor immunity by enhancing the effector to regulatory T cell ratio. The signature of ICOSL+ B cells is imprinted by complement-CR2 signaling, which is triggered by immunogenic cell death. Moreover, we identified that CD55, a complement inhibitory protein, determines the opposite roles of B cells in chemotherapy. Collectively, we demonstrated a critical role of the B cell subset switch in chemotherapy response, which has implications in designing novel anti-cancer therapies. VIDEO ABSTRACT.

Tumour circular RNAs elicit anti-tumour immunity by encoding cryptic peptides.

Emerging data have shown that previously defined noncoding genomes might encode peptides that bind human leukocyte antigen (HLA) as cryptic antigens to stimulate adaptive immunity1,2. However, the significance and mechanisms of action of cryptic antigens in anti-tumour immunity remain unclear. Here mass spectrometry of the HLA class I (HLA-I) peptidome coupled with ribosome sequencing of human breast cancer samples identified HLA-I-binding cryptic antigenic peptides that were noncanonically translated by a tumour-specific circular RNA (circRNA): circFAM53B. The cryptic peptides efficiently primed naive CD4+ and CD8+ T cells in an antigen-specific manner and induced anti-tumour immunity. Clinically, the expression of circFAM53B and its encoded peptides was associated with substantial infiltration of antigen-specific CD8+ T cells and better survival in patients with breast cancer and patients with melanoma. Mechanistically, circFAM53B-encoded peptides had strong binding affinity to both HLA-I and HLA-II molecules. In vivo, administration of vaccines consisting of tumour-specific circRNA or its encoded peptides in mice bearing breast cancer tumours or melanoma induced enhanced infiltration of tumour-antigen-specific cytotoxic T cells, which led to effective tumour control. Overall, our findings reveal that noncanonical translation of circRNAs can drive efficient anti-tumour immunity, which suggests that vaccination exploiting tumour-specific circRNAs may serve as an immunotherapeutic strategy against malignant tumours.

Noncoding RNAs in skeletal development and disorders.

Protein-encoding genes only constitute less than 2% of total human genomic sequences, and 98% of genetic information was previously referred to as "junk DNA". Meanwhile, non-coding RNAs (ncRNAs) consist of approximately 60% of the transcriptional output of human cells. Thousands of ncRNAs have been identified in recent decades, and their essential roles in the regulation of gene expression in diverse cellular pathways associated with fundamental cell processes, including proliferation, differentiation, apoptosis, and metabolism, have been extensively investigated. Furthermore, the gene regulation networks they form modulate gene expression in normal development and under pathological conditions. In this review, we integrate current information about the classification, biogenesis, and function of ncRNAs and how these ncRNAs support skeletal development through their regulation of critical genes and signaling pathways in vivo. We also summarize the updated knowledge of ncRNAs involved in common skeletal diseases and disorders, including but not limited to osteoporosis, osteoarthritis, rheumatoid arthritis, scoliosis, and intervertebral disc degeneration, by highlighting their roles established from in vivo, in vitro, and ex vivo studies.

EuRBPDB: a comprehensive resource for annotation, functional and oncological investigation of eukaryotic RNA binding proteins (RBPs).

RNA binding proteins (RBPs) are a large protein family that plays important roles at almost all levels of gene regulation through interacting with RNAs, and contributes to numerous biological processes. However, the complete list of eukaryotic RBPs including human is still unavailable. Here, we systematically identified RBPs in 162 eukaryotic species based on both computational analysis of RNA binding domains (RBDs) and large-scale RNA binding proteomic data, and established a comprehensive eukaryotic RBP database, EuRBPDB (http://EuRBPDB.syshospital.org). We identified a total of 311 571 RBPs with RBDs (corresponding to 6368 ortholog groups) and 3,651 non-canonical RBPs without known RBDs. EuRBPDB provides detailed annotations for each RBP, including basic information and functional annotation. Moreover, we systematically investigated RBPs in the context of cancer biology based on published literatures, PPI-network and large-scale omics data. To facilitate the exploration of the clinical relevance of RBPs, we additionally designed a cancer web interface to systematically and interactively display the biological features of RBPs in various types of cancers. EuRBPDB has a user-friendly web interface with browse and search functions, as well as data downloading function. We expect that EuRBPDB will be a widely-used resource and platform for both the communities of RNA biology and cancer biology.

The subunit of RNA N6-methyladenosine methyltransferase OsFIP regulates early degeneration of microspores in rice.

N6-Methyladenosine (m6A) RNA methylation plays important roles during development in different species. However, knowledge of m6A RNA methylation in monocots remains limited. In this study, we reported that OsFIP and OsMTA2 are the components of m6A RNA methyltransferase complex in rice and uncovered a previously unknown function of m6A RNA methylation in regulation of plant sporogenesis. Importantly, OsFIP is essential for rice male gametogenesis. Knocking out of OsFIP results in early degeneration of microspores at the vacuolated pollen stage and simultaneously causes abnormal meiosis in prophase I. We further analyzed the profile of rice m6A modification during sporogenesis in both WT and OsFIP loss-of-function plants, and identified a rice panicle specific m6A modification motif "UGWAMH". Interestingly, we found that OsFIP directly mediates the m6A methylation of a set of threonine protease and NTPase mRNAs and is essential for their expression and/or splicing, which in turn regulates the progress of sporogenesis. Our findings revealed for the first time that OsFIP plays an indispensable role in plant early sporogenesis. This study also provides evidence for the different functions of the m6A RNA methyltransferase complex between rice and Arabidopsis.

Reprogramming of m6A epitranscriptome is crucial for shaping of transcriptome and proteome in response to hypoxia.

Hypoxia causes a series of responses supporting cells to survive in harsh environments. Substantial post-transcriptional and translational regulation during hypoxia has been observed. However, detailed regulatory mechanism in response to hypoxia is still far from complete. RNA m6A modification has been proven to govern the life cycle of RNAs. Here, we reported that total m6A level of mRNAs was decreased during hypoxia, which might be mediated by the induction of m6A eraser, ALKBH5. Meanwhile, expression levels of most YTH family members of m6A readers were systematically down-regulated. Transcriptome-wide analysis of m6A revealed a drastic reprogramming of m6A epitranscriptome during cellular hypoxia. Integration of m6A epitranscriptome with either RNA-seq based transcriptome analysis or mass spectrometry (LC-MS/MS) based proteome analysis of cells upon hypoxic stress revealed that reprogramming of m6A epitranscriptome reshaped the transcriptome and proteome, thereby supporting efficient generation of energy for adaption to hypoxia. Moreover, ATP production was blocked when silencing an m6A eraser, ALKBH5, under hypoxic condition, demonstrating that m6A pathway is an important regulator during hypoxic response. Collectively, our studies indicate that crosstalk between m6A and HIF1 pathway is essential for cellular response to hypoxia, providing insights into the underlying molecular mechanisms during hypoxia.

Overexpression of lncRNAs with endogenous lengths and functions using a lncRNA delivery system based on transposon.

BACKGROUND: Long noncoding RNAs (lncRNAs) play important roles in many physiological and pathological processes, this indicates that lncRNAs can serve as potential targets for gene therapy. Stable expression is a fundamental technology in the study of lncRNAs. The lentivirus is one of the most widely used delivery systems for stable expression. However, it was initially designed for mRNAs, and the applicability of lentiviral vectors for lncRNAs is largely unknown. RESULTS: We found that the lentiviral vector produces lncRNAs with improper termination, appending an extra fragment of ~ 2 kb to the 3'-end. Consequently, the secondary structures were changed, the RNA-protein interactions were blocked, and the functions were impaired in certain lncRNAs, which indicated that lentiviral vectors are not ideal delivery systems of lncRNAs. Here, we developed a novel lncRNA delivery method called the Expression of LncRNAs with Endogenous Characteristics using the Transposon System (ELECTS). By inserting a termination signal after the lncRNA sequence, ELECTS produces transcripts without 3'-flanking sequences and retains the native features and function of lncRNAs, which cannot be achieved by lentiviral vectors. Moreover, ELECTS presents no potential risk of infection for the operators and it takes much less time. ELECTS provides a reliable, convenient, safe, and efficient delivery method for stable expression of lncRNAs. CONCLUSIONS: Our study demonstrated that improper transcriptional termination from lentiviral vectors have fundamental effects on molecular action and cellular function of lncRNAs. The ELECTS system developed in this study will provide a convenient and reliable method for the lncRNA study.

Circular RNA MAPK4 (circ-MAPK4) inhibits cell apoptosis via MAPK signaling pathway by sponging miR-125a-3p in gliomas.

BACKGROUND: Recent evidences have shown that circular RNAs (circRNAs) are frequently dysregulated and play paramount roles in various cancers. circRNAs are abundant in central nervous system (CNS); however, few studies describe the clinical significance and role of circRNAs in gliomas, which is the most common and aggressive primary malignant tumor in the CNS. METHODS: A bioinformatics analysis was performed to profile and screen the dyregulated circRNAs during early neural development. Quantitative real-time PCR was used to detect the expression of circ-MAPK4 and target miRNAs. Glioma cells were transfected with circ-MAPK4 siRNAs, then cell proliferation, apoptosis, transwell assays, as well as tumorigenesis and TUNEL assays, were performed to examine effect of circ-MAPK4 in vitro and vivo. Biotinylated-circ-MAPK4 probe based pull-down assay was conducted to confirm the relationship between circ-MAPK4 and miR-125-3p. RESULTS: In this study, we identified a circRNA, circ-MAPK4 (has_circ_0047688), which was downregulated during early neural differentiation. In gliomas, circ-MAPK4 acted as an oncogene, was inversely upregulated and linked to clinical pathological stage of gliomas (P < 0.05). Next, we verified that circ-MAPK4 promoted the survival and inhibited the apoptosis of glioma cells in vitro and in vivo. Furthermore, we proved that circ-MAPK4 was involved in regulating p38/MAPK pathway, which affected glioma proliferation and apoptosis. Finally, miR-125a-3p, a miRNA exhibited tumor-suppressive function through impairing p38/MAPK pathway, which was increased by inhibiting circ-MAPK4 and could be pulled down by circ-MAPK4. Inhibition of miR-125a-3p could partly rescue the increased phosphorylation levels of p38/MAPK and the elevated amount of apoptosis inducing by knockdown of circ-MAPK4. CONCLUSIONS: Our findings suggest that circ-MAPK4 is a critical player in glioma cell survival and apoptosis via p38/MAPK signaling pathway through modulation of miR-125a-3p, which can serve as a new therapeutic target for treatment of gliomas.

CIRDES: an efficient genome-wide method for in vivo RNA-RNA interactome analysis.

Complex RNA-RNA interactions underlie fundamental biological processes. However, a large number of RNA-RNA interactions remain unknown. Most existing methods used to map RNA-RNA interactions are based on proximity ligation, but these strategies also capture a huge amount of intramolecular RNA secondary structures, making it almost impossible to detect most RNA-RNA interactions. To overcome this limitation, we developed an efficient, genome-wide method, Capture Interacting RNA and Deep Sequencing (CIRDES) for in vivo capturing of the RNA interactome. We designed multiple 20-nt CIRDES probes tiling the whole RNA sequence of interest. This strategy obtained high selectivity and low background noise proved by qRT-PCR data. CIRDES enriched target RNA and its interacting RNAs from cells crosslinked by formaldehyde in high efficiency. After hybridization and purification, the captured RNAs were converted to the cDNA library after a highly efficient ligation to a 3' end infrared-dye-conjugated RNA adapter based on adapter ligation library construction. Using CIRDES, we detected highly abundant known interacting RNA, as well as a large number of novel targets of U6 snRNA. The enrichment of U4 snRNA, which interacts with U6, confirmed the robustness of the identification of the RNA-RNA interaction by CIRDES. These results suggest that the CIRDES is an efficient strategy for genome-wide RNA-RNA interactome analysis.

Deep sequencing reveals a global reprogramming of lncRNA transcriptome during EMT.

Several studies have shown that long non-coding RNAs (lncRNAs) may play an essential role in Epithelial-Mesenchymal Transition (EMT), which is an important step in tumor metastasis; however, little is known about the global change of lncRNA transcriptome during EMT. To investigate how lncRNA transcriptome alterations contribute to EMT progression regulation, we deep-sequenced the whole-transcriptome of MCF10A as the cells underwent TGF-ß-induced EMT. RESULTS: Deep-sequencing results showed that the long RNA transcriptome of MCF10A had undergone global changes as early as 8h after treatment with TGF-ß. The expression of 3403 known and novel lncRNAs, and 570 known and novel circRNAs were altered during EMT. To identify the key lncRNA-regulator, we constructed the co-expression network and found all junction nodes in the network are lncRNAs. One junction node, RP6-65G23.5, was further verified as a key regulator of EMT. Intriguingly, we identified 216 clusters containing lncRNAs which were located in "gene desert" regions. The expressions of all lncRNAs in these clusters changed concurrently during EMT, strongly suggesting that these clusters might play important roles in EMT. Our study reveals a global reprogramming of lncRNAs transcriptome during EMT and provides clues for the future study of the molecular mechanism of EMT.

Both endo-siRNAs and tRNA-derived small RNAs are involved in the differentiation of primitive eukaryote Giardia lamblia.

Small RNAs (sRNAs), including microRNAs and endogenous siRNAs (endo-siRNAs), regulate most important biologic processes in eukaryotes, such as cell division and differentiation. Although sRNAs have been extensively studied in various eukaryotes, the role of sRNAs in the early emergence of eukaryotes is unclear. To address these questions, we deep sequenced the sRNA transcriptome of four different stages in the differentiation of Giardia lamblia, one of the most primitive eukaryotes. We identified a large number of endo-siRNAs in this fascinating parasitic protozoan and found that they were produced from live telomeric retrotransposons and three genomic regions (i.e., endo-siRNA generating regions [eSGRs]). eSGR-derived endo-siRNAs were proven to target mRNAs in trans. Gradual up-regulation of endo-siRNAs in the differentiation of Giardia suggested that they might be involved in the regulation of this process. This hypothesis was supported by the impairment of the differentiation ability of Giardia when GLDICER, essential for the biogenesis of endo-siRNAs, was knocked down. Endo-siRNAs are not the only sRNA regulators in Giardia differentiation, because a great number of tRNAs-derived sRNAs showed more dramatic expression changes than endo-siRNAs in this process. We totally identified five novel kinds of tRNAs-derived sRNAs and found that the biogenesis in four of them might be correlated with that of stress-induced tRNA-derived RNA (sitRNA), which was discovered in our previous studies. Our studies reveal an unexpected complex panorama of sRNA in G. lamblia and shed light on the origin and functional evolution of eukaryotic sRNAs.

Comparative transcriptome analysis of small noncoding RNAs in different stages of Trypanosoma brucei.

Trypanosoma brucei, a pathogen of human and domestic animals, is an early evolved parasitic protozoan with a complex life cycle. Most genes of this parasite are post-transcriptionally regulated. However, the mechanisms and the molecules involved remain largely unknown. We have deep-sequenced the small RNAs of two life stages of this parasite--the bloodstream form and the procyclic form. Our results show that the small RNAs of T. brucei could derive from multiple sources, including NATs (natural antisense transcripts), tRNAs, and rRNAs. Most of these small RNAs in the two stages were found to share uniform characteristics. However, our results demonstrate that their variety and expression show significant differences between different stages, indicating possible functional differentiation. Dicer-knockdown evidence further proved that some of the small interfering RNAs (siRNAs) could regulate the expression of genes. Based on the genome-wide analysis of the small RNAs in the two stages of T. brucei, our results not only provide evidence to study their differentiation but also shed light on questions regarding the origins and evolution of small RNA-based mechanisms in early eukaryotes.

Pseudogene-derived small interference RNAs regulate gene expression in African Trypanosoma brucei.

Pseudogenes have been shown to acquire unique regulatory roles from more and more organisms. We report the observation of a cluster of siRNAs derived from pseudogenes of African Trypanosoma brucei using high through-put analysis. We show that these pseudogene-derived siRNAs suppress gene expression through RNA interference. The discovery that siRNAs may originate from pseudogenes and regulate gene expression in a unicellular eukaryote provides insights into the functional roles of pseudogenes and into the origin of noncoding small RNAs.

Glycolysis and tumor progression promoted by the m6A writer VIRMA via m6A-dependent upregulation of STRA6 in pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive and lethal malignancies, highlighting the urgent need to elucidate the underlying oncogenic mechanisms. VIRMA is a classic isoform of methyltransferases that participates in epigenetic transcriptomic modification in eukaryotic mRNAs. However, the exact roles of VIRMA in PDAC remain unclear. Here, we identified that VIRMA is highly expressed in PDAC, and histone modifications of the promoter may partly account for this dysregulation. Moreover, VIRMA is closely related to glycolysis and poor prognosis in PDAC. We further determined that STRA6 is a direct downstream target of VIRMA in PDAC by RNA sequencing (RNA-seq) and m6A sequencing (m6A-seq). VIRMA is involved in gene expression regulation via 3' UTR targeting of STRA6 mRNA. Furthermore, the m6A reader IGF2BP2 was shown to critically contribute to the stability of STRA6 mRNA. We describe the role of VIRMA in promoting signaling via the STRA6/STAT3 axis, which results in increased levels of HIF-1α, a key activator of glycolysis. In vivo and in vitro experiments reveal that the VIRMA-STRA6-STAT3-HIF-1α axis plays an instrumental role in glycolysis and tumor progression in PDAC. In conclusion, we demonstrate that VIRMA can increase glycolysis in PDAC by upregulating STRA6, a cell surface membrane protein that stimulates the STAT3 pathway, thereby activating HIF-1α and leading to pancreatic cancer malignancy. Overall, our data strongly suggest that the VIRMA-STRA6-STAT3-HIF-1α axis is a viable therapeutic target in PDAC.

Niche stiffness sustains cancer stemness via TAZ and NANOG phase separation.

Emerging evidence shows that the biomechanical environment is required to support cancer stem cells (CSCs), which play a crucial role in drug resistance. However, how mechanotransduction signals regulate CSCs and its clinical significance has remained unclear. Using clinical-practice ultrasound elastography for patients' lesions and atomic force microscopy for surgical samples, we reveal that increased matrix stiffness is associated with poor responses to neoadjuvant chemotherapy, worse prognosis, and CSC enrichment in patients with breast cancer. Mechanically, TAZ activated by biomechanics enhances CSC properties via phase separation with NANOG. TAZ-NANOG phase separation, which is dependent on acidic residues in the N-terminal activation domain of NANOG, promotes the transcription of SOX2 and OCT4. Therapeutically, targeting NANOG or TAZ reduces CSCs and enhances the chemosensitivity in vivo. Collectively, this study demonstrated that the phase separation of a pluripotency transcription factor links mechanical cues in the niche to the fate of CSCs.

CD146 promotes malignant progression of breast phyllodes tumor through suppressing DCBLD2 degradation and activating the AKT pathway.

BACKGROUND: As a rapid-progressing tumor, breast malignant phyllodes tumors (PTs) are challenged by the lack of effective therapeutic strategies and suitable prognostic markers. This study aimed to clarify the role and mechanism of CD146 on promoting PTs malignant progression, and to identify a novel prognosis marker and treatment target of breast malignant PTs. METHODS: The expression and prognostic significance of CD146 in PTs was detected through single-cell RNA-sequencing (scRNA-seq), immunostaining, real-time PCR and other methodologies. Functional experiments including proliferation assay, colony formation assay, transwell assay, and collagen contraction assay were conducted to validate the role of CD146 in malignant progression of PTs. The efficacy of anti-CD146 monoclonal antibody AA98 against malignant PTs was corroborated by a malignant PT organoid model and a PT patient-derived xenograft (PDX) model. Transcriptome sequencing, proteomic analysis, co-immunoprecipitation, and pull-down assay was employed to identify the modulating pathway and additional molecular mechanism. RESULTS: In this study, the scRNA-seq analysis of PTs disclosed a CD146-positive characteristic in the α-SMA+ fibroblast subset. Furthermore, a progressive elevation in the level of CD146 was observed with the malignant progression of PTs. More importantly, CD146 was found to serve as an independent predictor for recurrence in PT patients. Furthermore, CD146 was found to augment the viability and invasion of PTs. Mechanistically, CD146 acted as a protective "shield" to prevent the degradation of Discoidin, CUB, and LCCL domain-containing protein 2 (DCBLD2), thereby activating the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway and enhancing malignant behaviors of PT cells. In the malignant PT organoid and PDX model, a significant suppression of malignant PT growth was observed after the application of AA98. CONCLUSIONS: These findings suggested that CD146 served as an efficacious marker for predicting PT malignant progression and showed promise as a prognosis marker and treatment target of breast malignant PTs. The study further unveiled the essential role of the CD146-DCBLD2/PI3K/AKT axis in the malignant progression of PTs.

Drastic expression change of transposon-derived piRNA-like RNAs and microRNAs in early stages of chicken embryos implies a role in gastrulation.

Recent studies have shown that endogenous small RNAs regulate a variety of biological processes during vertebrate development; however, little is known about the role of small RNAs in regulating developmental signaling pathways during early embryogenesis. In this study, we applied Illumina sequencing to characterize an unexpected endogenous small RNA catalog and demonstrated a dramatic transition from transposon-derived piRNA-like small RNAs (pilRNAs) to microRNAs (miRNAs) in pre- and post-gastrula chicken embryos. The comprehensive expression profile of chicken miRNAs at the pre- and post-gastrula stages revealed that most known and new miRNAs were dynamically regulated during development. In addition to embryonic stem cell-related miRNAs, Gene Ontology (GO) analysis showed that miRNAs enriched in early stage chicken embryos targeted multiple signal transduction pathways associated with the reproductive process and embryogenesis, including Wnt and TGF-ß, which specifies the neural fate of blastodermal cells. Intriguingly, a large cohort of pilRNAs primarily derived from the active and most abundant transposable elements (TEs) were enriched in chicken stage X blastoderms. Within stage X blastoderms, pilRNAs were specifically localized to the primordial germ cells (PGCs), indicating their post-zygotic origin. Together, these findings imply a role for small RNAs in gastrulation in early stage chicken embryos.

RNA-binding protein MEX3A controls G1/S transition via regulating the RB/E2F pathway in clear cell renal cell carcinoma.

MEX3A is an RNA-binding protein that mediates mRNA decay through binding to 3' untranslated regions. However, its role and mechanism in clear cell renal cell carcinoma remain unknown. In this study, we found that MEX3A expression was transcriptionally activated by ETS1 and upregulated in clear cell renal cell carcinoma. Silencing MEX3A markedly reduced clear cell renal cell carcinoma cell proliferation in vitro and in vivo. Inhibiting MEX3A induced G1/S cell-cycle arrest. Gene set enrichment analysis revealed that E2F targets are the central downstream pathways of MEX3A. To identify MEX3A targets, systematic screening using enhanced cross-linking and immunoprecipitation sequencing, and RNA-immunoprecipitation sequencing assays were performed. A network of 4,000 genes was identified as potential targets of MEX3A. Gene ontology analysis of upregulated genes bound by MEX3A indicated that negative regulation of the cell proliferation pathway was highly enriched. Further assays indicated that MEX3A bound to the CDKN2B 3' untranslated region, promoting its mRNA degradation. This leads to decreased levels of CDKN2B and an uncontrolled cell cycle in clear cell renal cell carcinoma, which was confirmed by rescue experiments. Our findings revealed that MEX3A acts as a post-transcriptional regulator of abnormal cell-cycle progression in clear cell renal cell carcinoma.