Project description:RBM15, an RNA binding protein, determines cell-fate specification of many tissues including blood. We demonstrate that RBM15 is methylated by protein arginine methyltransferase 1 (PRMT1) at residue R578 leading to its degradation via ubiquitylation by an E3 ligase (CNOT4). Overexpression of PRMT1 in acute megakaryocytic leukemia cell lines blocks megakaryocyte terminal differentiation by downregulation of RBM15 protein level. Restoring RBM15 protein level rescues megakaryocyte terminal differentiation blocked by PRMT1 overexpression. At the molecular level, RBM15 binds to pre-mRNA intronic regions of genes important for megakaryopoiesis such as GATA1, RUNX1, TAL1 and c-MPL. Furthermore, preferential binding of RBM15 to specific intronic regions recruits the splicing factor SF3B1 to the same sites for alternative splicing. Therefore, PRMT1 regulates alternative RNA splicing via reducing RBM15 protein concentration. Targeting PRMT1 may be a curative therapy to restore megakaryocyte differentiation for acute megakaryocytic leukemia.
Project description:PRMT1 is highly expressed in breast tumors, and has been suggested to play a vital role in breast tumorigenesis, but the underlying molecular mechanisms remain to be fully characterized. Here, we reveal that PRMT1 exhibits a wide-spreading role in RNA alternative splicing based on transcriptome analysis, with a preference for exon inclusion in a large cohort of oncogenic genes. Profiling PRMT1 methylome reveals that the arginine/serine-rich splicing factor SRSF1 is heavily arginine-methylated by PRMT1, which is critical for SRSF1 phosphorylation, SRSF1 binding with RNA, and PRMT1-induced exon inclusion. In breast tumors, the overexpression of PRMT1 is associated with high levels of SRSF1 arginine methylation and aberrant exon inclusion in those oncogenic genes. Accordingly, PRMT1-mediated SRSF1 methylation and exon inclusion events are found to be critical for the malignant behaviors of breast cancer cells. Furthermore, we identified and characterized a selective PRMT1 inhibitor iPRMT1, which is potent in inhibiting PRMT1-mediated SRSF1 methylation and exon inclusion events, and breast cancer cell growth both in vitro and in vivo. Combination treatment with iPRMT1 and inhibitor targeting SRSF1 phosphorylation, SPHINX31 or SRPIN340, exhibits synergistic effects on suppressing breast cancer cell growth, strengthening the cross-talk between arginine methylation and phosphorylation in SRSF1. In conclusion, our data uncover a key mechanism underlying PRMT1-mediated gene alternative splicing, demonstrating targeting PRMT1 has great potential to treat breast cancer in clinic.
Project description:Cross-talk between distinct protein post-translational modifications is critical for an effective DNA damage response. Arginine methylation plays an important role in maintaining genome stability, however how this modification integrates with other enzymatic activities is largely unknown. Here, we identify the deubiquitylating enzyme USP11 as a previously uncharacterised PRMT1 substrate, and that methylation of USP11 promotes DNA end-resection and the repair of DNA double strand breaks by homologous recombination (HR). In addition, we show that PRMT1 is a ubiquitylated protein that it is targeted for deubiquitylation by USP11, and that USP11 regulates the ability of PRMT1 to bind to and methylate MRE11. Interestingly, USP11 methylation by PRMT1 is not required for other USP11 activities during HR, such as PALB2 deubiquitylation. Taken together, our findings reveal a specific role for USP11 during the early stages of DSB repair, which is mediated through its ability to regulate the activity of the PRMT1-MRE11 pathway.
Project description:Ubiquitylation of H2B on lysine 120 (H2Bub) is associated with active transcriptional elongation. H2Bub has been implicated in histone cross-talk and is generally regarded to be a prerequisite for H3K4 and H3K79 tri-methylation in both yeast and mammalian cells. We performed a genome-wide analysis of epigenetic marks during muscle differentiation, and, strikingly, we observed a near-complete loss of H2Bub in the differentiated state. We examined the basis for global loss of this mark and found that the H2B ubiquitin E3 ligase, RNF20, was depleted from chromatin in differentiated myotubes, indicating that recruitment of this protein to genes substantially decreases upon differentiation. Remarkably, during the course of myogenic differentiation, we observed retention and acquisition of H3K4 tri-methylation on a large number of genes in the absence of detectable H2Bub. The Set1 H3K4 trimethylase complex was efficiently recruited to a subset of genes in myotubes in the absence of detectable H2Bub, accounting in part for H3K4 tri-methylation in myotubes. Our studies suggest that H3K4me3 deposition in the absence of detectable H2Bub in myotubes is mediated via Set1 and, perhaps, MLL complexes, whose recruitment does not require H2Bub. Thus, muscle cells represent a novel setting in which to explore mechanisms that regulate histone cross-talk. Mapping of H2Bub in growing myoblasts (MB) and fully differentiated myotubes (MT).
Project description:Protein arginine methyltransferase 1 (Prmt1) is known as the major Type-I protein arginine methyltransferase that deposits asymmetrical dimethylarginine (ADMA) in both histone and non-histone substrates. Nonetheless, how Prmt1 and its downstream signalling through substrate methylation function in the male germline development remains poorly understood. In this study, we discovered that Prmt1 is predominantly present in the spermatogonial population during mouse spermatogenesis. Using three Cre-mediated conditional Prmt1 knockout mouse lines, we observed that Prmt1 is essential for the maintenance of spermatogonial cells and Prmt1-deposited ADMA marks coordinate an inherent homeostasis among three types of substrate methylation. In conjunction with high-throughput Cut&Tag and modified mini-bulk Smart-seq2 analyses, we unveiled that Prmt1-mediated H4R3me2a mark enriched in the promoter region, together with other histone arginine methylations, drives a global transcriptomic landscape that maintains the regular gene expression and alternative splicing. Collectively, we provide the genetic evidence showing the essential role of Prmt1-deposited arginine methylation in the establishment of transcriptional homeostasis, and shed light on the methylarginine signalling pathway in orchestrating spermatogonial development in the mammalian germline.
Project description:Protein methylation has been implicated in many important biological contexts including signaling, metabolism, and transcriptional control. Despite the importance of this post- translational modification, the global analysis of protein methylation by mass spectrometry-based proteomics has not been extensively studied due to the lack of robust, well-characterized techniques for methyl-peptidemethyl peptide enrichment. Here, to better investigate protein methylation, we optimized and compared two methods for methyl-peptidemethyl peptide enrichment: immunoaffinity purification (IAP) and high pH strong cation exchange (SCX). Comparison of these methods revealed that they are largely orthogonal for monomethyl arginine (MMA), suggesting that the usage of both techniques is required to provide a global view of protein methylation. Using both IAP and SCX, we investigated changes in protein methylation downstream of protein arginine methyltransferase 1 (PRMT1). Together, these techniques allowed us to quantify over ~1,000 arginine methylation sites on 407 proteins. Of these methylation sites, PRMT1 knockdown resulted in significant changes to 110 arginine methylation sites on 59 proteins. In contrast, zero lysine methylation sites were significantly changed upon PRMT1 knockdown. In PRMT1 knockdown cells, 24 MMA sites exhibited both significant downregulation (ie, putative PRMT1-mediated MMA targets) and 63 significant upregulation (ie, putative PRMT1-mediated ADMA targets). PRMT1 knockdown induced significant changes in asymmetric dimethyl arginine (ADMA), consistent with being PRMT1 targets. Additionally, We also observed that PRMT1 knockdown induced significant increases in symmetric dimethyl arginine (SDMA) methylation, suggesting that loss of PRMT1 activity allows scavenging of PRMT1 substrates by Type II PRMTs. Analysis of the subcellular localization and protein function of the significantly changing methyl-proteins revealed that the majority of PRMT1 substrates are localized to the nucleus and involved in RNA and DNA binding. Taken together, our results suggest that deep protein methylation profiling by mass spectrometry requires orthogonal enrichment techniques, identify novel PRMT1 methylation targets, and highlight in order to understand the dynamic interplay between methyltransferases in mammalian cells.
Project description:Ubiquitylation of H2B on lysine 120 (H2Bub) is associated with active transcriptional elongation. H2Bub has been implicated in histone cross-talk and is generally regarded to be a prerequisite for H3K4 and H3K79 tri-methylation in both yeast and mammalian cells. We performed a genome-wide analysis of epigenetic marks during muscle differentiation, and, strikingly, we observed a near-complete loss of H2Bub in the differentiated state. We examined the basis for global loss of this mark and found that the H2B ubiquitin E3 ligase, RNF20, was depleted from chromatin in differentiated myotubes, indicating that recruitment of this protein to genes substantially decreases upon differentiation. Remarkably, during the course of myogenic differentiation, we observed retention and acquisition of H3K4 tri-methylation on a large number of genes in the absence of detectable H2Bub. The Set1 H3K4 trimethylase complex was efficiently recruited to a subset of genes in myotubes in the absence of detectable H2Bub, accounting in part for H3K4 tri-methylation in myotubes. Our studies suggest that H3K4me3 deposition in the absence of detectable H2Bub in myotubes is mediated via Set1 and, perhaps, MLL complexes, whose recruitment does not require H2Bub. Thus, muscle cells represent a novel setting in which to explore mechanisms that regulate histone cross-talk.
Project description:XIST is a long non-coding RNA (lncRNA) that mediates transcriptional silencing of X chromosome genes. Here we show that XIST is highly methylated with at least 78 N6-methyladenosine (m6A) residues, a reversible base modification whose function in lncRNAs is unknown. We show that m6A formation in XIST, as well as cellular mRNAs, is mediated by RBM15 and its paralog RBM15B, which bind the m6A-methylation complex and recruit it to specific sites in RNA. This results in methylation of adenosines in adjacent m6A consensus motifs. Furthermore, knockdown of RBM15 and RBM15B, or knockdown of the m6A methyltransferase METTL3 impairs XIST-mediated gene silencing. A systematic comparison of m6A-binding proteins shows that YTHDC1 preferentially recognizes m6A in XIST and is required for XIST function. Additionally, artificial tethering of YTHDC1 to XIST rescues XIST-mediated silencing upon loss of m6A. These data reveal a pathway of m6A formation and recognition required for XIST-mediated transcriptional repression. Three to four biological HEK293T replicates were used to perform iCLIP of endogenous YTH proteins, RBM15, and RBM15B. Crosslinking induced truncations were identified using CIMS-CITS pipeline.
Project description:We found that cardiomyocyte-specific PRMT1-deficient (PRMT1-cKO) mice showed dilated cardiomyopathy and aberrant cardiac alternative splicing. To identify novel cardiac splicing events, we performed a comprehensive analysis of gene expression changes in hearts of wildtype (WT) and PRMT1-cKO mice using RNA sequencing (RNA-Seq). To investigate differentially expressed genes (false discovery rate (FDR) p<0.05, fold change >2) between control and PRMT1-cKO mice, we performed pairwise comparisons of RNA-Seq data using the CLC Genomics Workbench software.
Project description:Protein arginine (R) methylation is a post-translational modification that has been shown to play a role in various biological processes, such as RNA splicing, DNA repair, immune response, signal transduction and tumor development. Here, we present a dataset of high-quality methylations obtained from several different heavy methyl SILAC (hmSILAC) experiments analyzed with a machine learning model that was trained to recognize hmSILAC doublets and show that this model allows for improved high-confidence identification of methyl-peptides. The results of our analysis of the interactions between R-methylated proteins further support the idea that this modification plays a role in modulating protein:protein interactions and suggest a potential new role of R methylation in immunity and macrophage metabolism. Moreover, we intersect the methyl-site dataset with a phosphosite dataset to investigate the cross-talk between R methylation and phosphorylation. Finally, we explore the application of hmSILAC to identify unconventional methylated residues on both histone and non-histone proteins.