ABSTRACT: cTag-PAPERCLIP Reveals Alternative Polyadenylation Promotes Cell-Type Specific Protein Diversity and Shifts Araf Isoforms with Microglia Activation
Project description:Alternative polyadenylation (APA) is a widespread mechanism for gene regulation and has been implicated in flowering, but the molecular basis governing the choice of a specific poly(A) site during the vegetative-to-reproductive growth transition remains unclear. Here we characterize HLP1, an hnRNP A/B protein as a novel regulator for pre-mRNA 3’ end processing in Arabidopsis. Genetic analysis reveals that HLP1 suppresses Flowering Locus C (FLC), a key repressor of flowering in Arabidopsis. Genome-wide mapping of HLP1-RNA interactions indicates that HLP1 binds preferentially to A-rich and U-rich elements around cleavage and polyadenylation sites, implicating a role in 3’-end formation. We show significantly enriched binding of HLP1 to transcripts involved in RNA metabolism and flowering. Comprehensive profiling of the poly(A) site usage reveals that HLP1 mutations cause thousands of poly(A) site shifts. A distal-to-proximal poly(A) site shift in the flowering regulator FCA, a direct target of HLP1, further leading to up-regulated FLC and delayed flowering. Our results elucidate that HLP1 is a novel factor involved in 3’ end processing and controls reproductive timing via targeted APA. Investigate the role of HLP1 in Alternative Polyadenylation Contributed by: The Institute of Genetics and Developmental Biology (IGDB) of the Chinese Academy of Sciences
Project description:Alternative polyadenylation (APA) has recently been recognized as a universal mechanism for gene regulation, but it remains unclear how APA is controlled. Here we report that the Arabidopsis thaliana Protein Arginine Methyltransferase 10 (AtPRMT10) regulates global APA with its protein partner HLP1, a conserved hnRNP A/B protein. HLP1 binds preferentially to A-rich and U-rich cis-elements around polyadenylation sites, thereby linking AtPRMT10 to the control of APA through protein-protein interactions. AtPRMT10 mutations cause significant proximal-to-distal poly(A) site shifts largely overlapping with those in hlp1-1 mutants. Proximal polyadenylation is maintained by AtPRMT10-directed methylation and is mediated in part by methylation of HLP1 at specific arginine residues. Our findings demonstrate that arginine methylation of an RNA-binding protein adds a novel layer of regulation to widespread alternative polyadenylation.
Project description:Alternative polyadenylation (APA) is increasingly recognized to regulate gene expression across different cell-types, but obtaining APA maps from individual cell-types typically requires prior purification, a stressful procedure that can itself alter cellular states. Here, we describe a new platform, cTag-PAPERCLIP, that generates APA profiles from single cell populations in intact tissues; cTag-PAPERCLIP requires no tissue dissociation and preserves transcripts in native states. Applying cTag-PAPERCLIP to profile four major cell-types in the mouse brain revealed common APA preferences between excitatory and inhibitory neurons distinct from astrocytes and microglia, regulated in part by neuron-specific RNA-binding proteins NOVA2 and PTBP2. We further identified a role of APA in switching Araf protein isoforms during microglia activation, impacting production of downstream inflammatory cytokines. Our results demonstrate the broad applicability of cTag-PAPERCLIP and a previously undiscovered role of APA in contributing to protein diversity between different cell-types and cellular states within the brain.
Project description:Mapping MBNL-regulated genome-wide alternative polyadenylation: We report that depletion of Mbnl proteins in mouse embryo fibroblasts (MEFs), DM mouse model quadriceps muscle, and DM-autopsy muscle tissue leads to mis-regulation of alternative polyadenylation We compared WT, Mbnl1/2KO, Mbnl1/2KO/3siRNA, and Mbnl1/2KO/scrambled siRNA MEFs (n=2 for each group) to evaluate alternative polyadenylation shifts that occur due to progressive loss of Mbnl proteins. We also compared WT (1 day old, and 4 months old, n=2 each) and HSALR mouse model (4 months old, n=2) of myotonic dystrophy for developmental alternative polyadenylation defects in myotonic dystrophy. Finally, we compared control and DM1 autopsy muscle tissues (n=3) for changes in alternative polyadenylation. We performed HITS-CLIP analysis of binding sites of Mbnl1, Mbnl2 and Mbnl3 in MEFs (n=3 each). We also performed HITS-CLIP analysis for major skeletal muscle Mbnl protein, Mbnl1 in FVB WT adult muscle (4 months, n=3). Finally we performed HITS-CLIP analysis for CPSF6 in WT and Mbnl1/2 KO MEFs (n=3 each) Please note that the 'readme_Table.txt' describes the contents of 'Table S*.xlsx' files, and the readme_method.txt include additional details about experiemenal procedures.
Project description:Cell-type-specific gene regulatory programs are crucial for cell differentiation and function. In animal neurons, the highly conserved ELAV/Hu family of proteins promotes alternative splicing and alternative polyadenylation of mRNA precursors to create unique neuronal transcript isoforms. Here, we show in Drosophila that the ELAV-mediated establishment of neuron-specific mRNA isoforms at the onset of neuronal differentiation constitutes a developmental bottleneck. While ELAV loss during a critical developmental time window is lethal and cannot be rescued later by the activation of the ELAV-like paralogue FNE, loss of ELAV function outside of that window results in neurological defects of differing nature and degree. FNE can effectively perform all molecular functions of ELAV, and, when activated early enough, fully rescue neuronal development. Our findings demonstrate the essential role of robust ELAV activity and intact neuronal signatures in the differentiation and function of the nervous system.
Project description:In eukaryotes, the 3' ends of RNA polymerase II-generated transcripts are made in the majority of cases by site-specific endonucleolytic cleavage, followed by the addition of a poly(A) tail. By alternative polyadenylation, a gene can give rise to multiple mRNA isoforms that differ in the length of their 3' UTRs and hence in their susceptibility to post-transcriptional regulatory factors such as microRNAs. A series of recently conducted high-throughput studies of poly(A) site usage revealed an extensive tissue-specific control of 3’ UTR length and drastic changes in 3’ UTR length of mRNAs upon induction of proliferation in resting cells. To understand the dynamics of polyadenylation site usage, we recently identified binding sites of the major pre-mRNA 3’ end processing factors - cleavage and polyadenylation specificity factor (CPSF), cleavage stimulation factor (CstF), and cleavage factor Im (CF Im) - and mapped cleaved polyadenylation sites in HEK293 cells. Our present study extends previous findings on the role of CF Im in alternative polyadenylation and reveals that subunits of the CF Im complex generally control 3’ UTR length. More specifically, we demonstrate that the loss-of-function of CF Im68 and CF Im25 but not of CF Im59 leads to a transcriptome-wide increase of the use of proximal polyadenylation sites. 3' ends of transcripts were profiled by high-throughput sequencing in HEK 293 cells under normal conditions, and in HEK 293 cells depleted of 3' end processing factors CF Im25, CF Im59, and CF Im68.
Project description:The tumorigenesis of small intestinal neuroendocrine tumors (NETs) is poorly understood. Recent studies have associated alternative polyadenylation with proliferation, cell transformation and cancer. Polyadenylation is the process in which the pre-mRNA is cleaved at a polyA site and a polyA tail is added. Genes with two or more polyA sites can undergo alternative polyadenylation. This produces two or more distinct mRNA isoforms with different 3M-bM-^@M-^Y untranslated regions. Additionally, alternative polyadenylation can also produce mRNAs containing different 3M-bM-^@M-^Y-terminal coding regions. Therefore, alternative polyadenylation alters both the repertoire and the expression level of proteins. Here we used high-throughput sequencing data to map polyA sites and characterize polyadenylation genome-wide in three small intestinal neuroendocrine tumors and a reference sample. In the tumors sixteen genes showed significant changes of alternative polyadenylation pattern, which lead to either the 3M-bM-^@M-^Y truncation of mRNA coding regions or 3M-bM-^@M-^Y untranslated regions. Among these, 11 genes had been previously associated with cancer, with 4 genes being known tumor suppressors: DCC, PDZD2, MAGI1 and DACT2. We validated the alternative polyadenylation in 3 out of 3 cases with Q-RT-PCR. Our findings suggest that changes of alternative polyadenylation pattern in these 16 genes could be involved in the tumorigenesis of small intestinal neuroendocrine tumors. Furthermore, they also point to alternative polyadenylation as a new target for both diagnostic and treatment of small intestinal neuroendocrine tumors. The identified genes with alternative polyadenylation specific to the small intestinal neuroendocrine tumors could be further tested as diagnostic markers and drug targets for disease prevention and treatment. PolyA-seq profiling of 3 human neuroendocrine tumors compared and pituitary using Direct RNA Sequencing from Helicos Biosciences Technology
Project description:Alternative polyadenylation generates numerous 3’ mRNA isoforms that can differ in their stability, structure, and function. These isoforms can be used to map mRNA stabilizing and destabilizing elements within 3’ untranslated regions (3’UTRs). Here, we examine how environmental conditions affect 3’ mRNA isoform turnover and structure in yeast cells on a transcriptome scale. Isoform stability broadly increases when cells grow more slowly, with relative half-lives of most isoforms being well correlated across multiple conditions. Surprisingly, dimethyl sulfate probing reveals that individual 3’ isoforms have similar structures across different conditions, in contrast to the extensive structural differences that can exist between closely related isoforms in an individual condition. Unexpectedly, most mRNA stabilizing and destabilizing elements function only in a single growth condition. The genes associated with some classes of condition-specific stability elements are enriched for different functional categories, suggesting that regulated mRNA stability might contribute to adaptation to different growth environments. Condition-specific stability elements do not result in corresponding condition-specific changes in steady-state mRNA isoform levels. This observation is consistent with a compensatory mechanism between polyadenylation and stability, and it suggests that condition-specific mRNA stability elements might largely reflect condition-specific regulation of mRNA 3’ end formation.
Project description:The proper subcellular localization of RNAs and local translational regulation is crucial in highly compartmentalized cells, such as neurons. RNA localization is mediated by specific cis-regulatory elements usually found in mRNA 3'UTRs. Therefore, processes that generate alternative 3'UTRs – alternative splicing and polyadenylation – have the potential to diversify mRNA localization patterns in neurons. Here, we performed mapping of alternative 3'UTRs in neurites and soma isolated from mESC-derived neurons. Our analysis identified 593 genes with differentially localized 3'UTR isoforms. In particular, we have shown that two isoforms of Cdc42 gene with distinct functions in neuronal polarity are differentially localized between neurites and soma of mESC-derived and mouse primary cortical neurons, at both mRNA and protein level. Using reporter assays and 3'UTR swapping experiments, we have identified the role of alternative 3’UTRs and mRNA transport in differential localization of alternative CDC42 protein isoforms. Moreover, we used SILAC to identify isoform-specific Cdc42 3'UTR-bound proteome with potential role in Cdc42 localization and translation. Our analysis points to usage of alternative 3'UTR isoforms as a novel mechanism to provide for differential localization of functionally diverse alternative protein isoforms.
Project description:Alternative polyadenylation is an important cellular mechanism that enables generation of mRNA isoforms that differ in their 3' untranslated regions (3' UTRs) and consequently in their susceptibility to miRNA and RNA binding protein mediated regulation. A dramatic change in polyadenylation site usage, leading to the systematic expression of short 3’ UTR isoforms is known to occur upon induction of proliferation in resting cells. To understand the functional consequences of short 3’ UTR isoform expression we used 3' end sequencing and quantitative mass spectroscopy to determine polyadenylation site use, mRNA and protein levels in murine and human naive and activated T cells. We found that while the process and its impact on the susceptibility to miRNA and RNA binding protein mediated regulation are evolutionarily conserved, the conservation is poor at the level of individual orthologous genes. Contrary to the common belief, we did not find that transcriptome-wide 3' UTR shortening leads to a matched increase in mRNA and protein levels of genes with tandem polyadenylation sites. 3' ends of transcripts were profiled by high-throughput sequencing in murine and human naive and activated T cells.