Project description:The RNA methyltransferase Aly/REF export factor (ALYREF) is considered one type of “reader” protein located in the nucleus that recognizes and binds directly with m5C sites in RNA and facilitates the export of RNA from the nucleus to the cytoplasm. Notably, ALYREF is considered a promising target for diagnosis and prognosis prediction. However, until now, the low number of related studies has limited the understanding of the mechanism of the HCC-promoting effects of ALYREF. To further elucidate the oncogenic roles of ALYREF in hepatocellular carcinoma (HCC), we assessed the expression levels of ALYREF in clinical samples and HCC cell lines and explored the effects of ALYREF deficiency by both in vitro experiments and m5C-methylated RNA immunoprecipitation sequencing (m5C-MeRIP-Seq)
Project description:Methylation of carbon-5 of cytosines (m5C) is a conserved post-transcriptional nucleotide modification of RNA with widespread distribution across organisms. m5C has been shown to participate in mRNA transport and maintain mRNA stability through its recognition by the reader proteins ALYREF and YBX1, respectively. We recently showed that m5C is required for Caenorhabditis elegans development and fertility under heat stress. To contribute to the understanding of how m5C and its oxidative derivatives mediate their functions, we developed RNA baits bearing modified cytosines in diverse structural contexts to pulldown potential readers in C. elegans. Our mass spectrometry analyses reveal unique binding proteins for each of the modifications. We validate our dataset by demonstrating that the nematode ALYREF homologues ALY-1 and ALY-2 preferentially bind m5C in vitro. The dataset presented here serves as an important scientific resource that will support the discovery of new functions of m5C and its derivatives.
Project description:The TREX complex (TREX) plays key roles in nuclear export of mRNAs. However, little is known about its transcriptome-wide binding targets. We used individual cross-linking and immunoprecipitation (iCLIP) to identify the binding sites of ALYREF, an mRNA export adaptor in TREX, in human cells. As expected, iCLIP reads are mainly mapped to exons of mRNAs. Globally, ALYREF binding shows two apparent enrichments on the mRNA, one is near the 5’ end and the other is very close to the 3’ end. In addition, numerous middle exons harbor ALYREF binding sites. CBP80 and PABPN1 mainly affect ALYREF binding at the 5’ and the 3’ region, respectively. Interestingly, we found that the 3’ processing factor CstF64 directly interacts with ALYREF and is required for the overall binding of ALYREF on the mRNA. Sequence analysis led to the identification of multiple
Project description:we try to investigate the binding of ALYREF and NXF1 on histone mRNA when the cell treated with indicated siRNAs. ALYREF plays key roles in nuclear export of polyadenylated mRNAs and also modulates their 3' processing, but whether it is involved in regulating RNAs beyond polyadenylated mRNAs is unknown. The replication-dependent (RD) histone mRNAs are not polyadenylated, but end in a stem-loop (SL) structure. Here we demonstrate that ALYREF prevalently binds a region next to the SL on RD histone mRNAs. SL-binding protein (SLBP) directly interacts with ALYREF and ensures this binding. To examine how SLBP KD impact ALYREF distribution on the histone mRNA, we carried out ALYREF iCLIP in control and SLBP KD cells. To investigate the functional consequence for ALYREF binding on histone mRNAs, we isolated polyA+ and polyA- RNAs from control and ALYREF KD cells, and carried out RNA-seq separately.
Project description:Multiple epitranscriptomic maps of the RNA modification 5-methylcytosine (m5C) have been prepared, often diverging markedly from each other in terms of site abundance and identity. Differences in detection methods, data depth and analysis pipelines, but also biological factors underly much of this disparity. To address this, we re-analysed available datasets from five human cell lines and seven tissues, generated by the prevailing bisulfite RNA sequencing method, with a coherent m5C site calling pipeline. We used the resulting union list of 6,393 m5C sites called across the broader transcriptome to study site distribution, enzymology, interaction with RNA-binding proteins and molecular function. We confirmed prior observations such as predominance of m5C sites within mRNA exons, enrichment around start codons, and that the tRNA:m5C methyltransferases (MTases) NSUN2 and 6 are the main m5C ‘writers’ for mRNAs. Each NSUN enzyme recognises mRNA features that strongly resemble their respective canonical substrates. Assessing proximity between mRNA m5C sites and footprints of RNA-binding proteins reconfirmed the mRNA export factor ALYREF as an m5C ‘reader’ and identified new candidates for functional interactions, including the RNA helicases DDX3X, involved in mRNA translation, and UPF1, an mRNA decay factor. Experiments in HeLa cells lacking NSUN2 showed that this affected both, steady-state level and UPF1-binding to target mRNAs. Our studies emphasise the emerging diversity of both, m5C writers and readers, affecting mRNA function.
Project description:During gene expression, RNA export factors are mainly known for driving nucleocytoplasmic transport. While early studies suggested that the Exon Junction Complex (EJC) may provide a binding platform for them, subsequent work proposed that they are only recruited by the Cap-Binding Complex (CBC) to the 5’ end of RNAs, as part of the TREX complex. Using iCLIP, we show that the export receptor Nxf1 and two TREX subunits, Alyref and Chtop, are actually recruited to the whole mRNA co-transcriptionally via splicing but before 3’-end processing. Consequently, Alyref can alter splicing decisions and Chtop regulates alternative polyadenylation. Surprisingly, we observe that eIF4A3 stimulates Alyref deposition on single exon or spliced RNAs close to EJC sites. Additional experiments suggest that Alyref is recruited to the 5’-end of RNAs by CBC before binding RNAs near EJCs. Our study reveals mechanical insights into the co-transcriptional recruitment of mRNA export factors and how this shapes the human transcriptome.
Project description:During gene expression, RNA export factors are mainly known for driving nucleocytoplasmic transport. While early studies suggested that the Exon Junction Complex (EJC) may provide a binding platform for them, subsequent work proposed that they are only recruited by the Cap-Binding Complex (CBC) to the 5’ end of RNAs, as part of the TREX complex. Using iCLIP, we show that the export receptor Nxf1 and two TREX subunits, Alyref and Chtop, are actually recruited to the whole mRNA co-transcriptionally via splicing but before 3’-end processing. Consequently, Alyref can alter splicing decisions and Chtop regulates alternative polyadenylation. Surprisingly, we observe that eIF4A3 stimulates Alyref deposition on single exon or spliced RNAs close to EJC sites. Additional experiments suggest that Alyref is recruited to the 5’-end of RNAs by CBC before binding RNAs near EJCs. Our study reveals mechanical insights into the co-transcriptional recruitment of mRNA export factors and how this shapes the human transcriptome.
Project description:During gene expression, RNA export factors are mainly known for driving nucleocytoplasmic transport. While early studies suggested that the Exon Junction Complex (EJC) may provide a binding platform for them, subsequent work proposed that they are only recruited by the Cap-Binding Complex (CBC) to the 5’ end of RNAs, as part of the TREX complex. Using iCLIP, we show that the export receptor Nxf1 and two TREX subunits, Alyref and Chtop, are actually recruited to the whole mRNA co-transcriptionally via splicing but before 3’-end processing. Consequently, Alyref can alter splicing decisions and Chtop regulates alternative polyadenylation. Surprisingly, we observe that eIF4A3 stimulates Alyref deposition on single exon or spliced RNAs close to EJC sites. Additional experiments suggest that Alyref is recruited to the 5’-end of RNAs by CBC before binding RNAs near EJCs. Our study reveals mechanical insights into the co-transcriptional recruitment of mRNA export factors and how this shapes the human transcriptome.
Project description:Through deep RNA-seq of human monocyte-derived macrophages, we identified RP11-184M15.1, a human macrophage-specific lincRNA, to be highly induced in the cytoplasm of IL-4-stimulated macrophage. Preliminary data showed that treatment of IL-4-stimulated THP1 human macrophages with RP11-184M15.1 small interfering RNA (siRNA) repressed apoptosis of resolving macrophages, as shown by decreased Annexin V+ macrophages, and reduced protein expression of cleaved PARP. Biotinylated RP11-184M15.1 pulldown coupled with mass spectrometry indicated an interaction between RP11-184M15.1 and zinc finger RNA-binding protein (ZFR). RIP corroborated the proposed interaction between RP11-184M15.1 and ZFR. RNAInter revealed mRNAs predicted to interact with ZFR, and some of those genes (e.g., ALYREF, CCNYL1) were also differentially expressed in RNA-seq data of control versus RP11-184M15.1 knockdown in IL-4-stimulated THP1 macrophages. qPCR validated that ALYREF and CCNYL1 expression are reduced with RP11-184M15.1 knockdown. In contrast, with ZFR siRNA, ALYREF and CCNYL1 mRNA expressions were elevated. Thus, a hypothesis to be further tested is that RP11-184M15.1 interacts with ZFR to regulate mRNA stability in IL-4-stimulated macrophages. Nuclear RNA export factor 1 (NXF1) was also validated by RIP to interact with RP11-184M15.1. NXF1 is a known interacting partner of ALYREF in the transcription-export (TREX) complex. With RP11-184M15.1 knockdown, the protein level of ALYREF decreased, and Ingenuity Pathway Analysis (IPA) of RNA-seq data of control versus RP11-184M15.1 knockdown revealed that THO complex subunit 5 homolog (THOC5), another component of the TREX complex, may be an upstream regulator. In addition, past studies have revealed that ALYREF and NXF1 are involved in nuclear export of inflammatory mRNAs and proinflammatory macrophage phenotype, respectively. With RP11-184M15.1 knockdown, there was decreased expression of inflammatory macrophage-associated genes. It may be possible that RP11-184M15.1 functions in mRNA export, along with NXF1 and ALYREF.