Elevated pre-mRNA 3' end processing activity in cancer cells renders vulnerability to inhibition of cleavage and polyadenylation [QuantSeq-Pool]
Ontology highlight
ABSTRACT: Cleavage and polyadenylation (CPA) defines the 3’ end of almost all eukaryotic mRNAs. CPA inhibition, or CPAi, leads to transcriptional readthrough. Here, we show that the CPSF-73 inhibitor JTE-607 globally perturbs gene expression, especially for those with a high GC content and located in high gene density regions. Based on regulated alternative polyadenylation (APA) events, we found that more frequently used CPA sites are inhibited by JTE-607 to a greater extent. Consistently, cells with elevated CPA activities, as indicated by preferential usage of proximal APA sites, display greater transcriptional readthrough and gene expression disturbance upon JTE-607 treatment. Remarkably, overexpression of the core CPA factor FIP1 enhances global CPA activity in the cell and leads to greater JTE-607 sensitivity. Taken together, our data indicate that CPAi selectively impacts genes based on their genomic features and the CPA activity of a cell is a key determinant of sensitivity to CPAi.
Project description:Cleavage and polyadenylation (CPA) defines the 3’ end of almost all eukaryotic mRNAs. CPA inhibition, or CPAi, leads to transcriptional readthrough. Here, we show that the CPSF-73 inhibitor JTE-607 globally perturbs gene expression, especially for those with a high GC content and located in high gene density regions. Based on regulated alternative polyadenylation (APA) events, we found that more frequently used CPA sites are inhibited by JTE-607 to a greater extent. Consistently, cells with elevated CPA activities, as indicated by preferential usage of proximal APA sites, display greater transcriptional readthrough and gene expression disturbance upon JTE-607 treatment. Remarkably, overexpression of the core CPA factor FIP1 enhances global CPA activity in the cell and leads to greater JTE-607 sensitivity. Taken together, our data indicate that CPAi selectively impacts genes based on their genomic features and the CPA activity of a cell is a key determinant of sensitivity to CPAi.
Project description:Cleavage and polyadenylation (CPA) defines the 3’ end of almost all eukaryotic mRNAs. CPA inhibition, or CPAi, leads to transcriptional readthrough. Here, we show that the CPSF-73 inhibitor JTE-607 globally perturbs gene expression, especially for those with a high GC content and located in high gene density regions. Based on regulated alternative polyadenylation (APA) events, we found that more frequently used CPA sites are inhibited by JTE-607 to a greater extent. Consistently, cells with elevated CPA activities, as indicated by preferential usage of proximal APA sites, display greater transcriptional readthrough and gene expression disturbance upon JTE-607 treatment. Remarkably, overexpression of the core CPA factor FIP1 enhances global CPA activity in the cell and leads to greater JTE-607 sensitivity. Taken together, our data indicate that CPAi selectively impacts genes based on their genomic features and the CPA activity of a cell is a key determinant of sensitivity to CPAi.
Project description:To assess the impact of CPA inhibition by JTE-607 on intra-cell-line transcriptomic heterogeneity, we profiled two lung cancer cell lines treated with DMSO or JTE-607 by 3' tag-based single-cell RNA-seq with 10x Chromium. For data analysis, we performed transcriptome quantification at the PAS-based transcript level to generate a PAS-by-cell count matrix, and then investigate the effect of JTE-607 treatment on PAS usage pattern and cellular states.
Project description:Most eukaryotic genes harbor multiple cleavage and polyadenylation sites (PASs), leading to expression of alternative polyadenylation (APA) isoforms. APA regulation has been implicated in a diverse array of physiological and pathological conditions. While RNA sequencing tools that generate reads containing the PAS, named onSite reads, have been instrumental in identifying PASs, they have not been widely used. By contrast, a growing number of methods generate reads that are close to the PAS, named nearSite reads, including the 3’ end counting strategy commonly used in single cell analysis. How these nearSite reads can be used for APA analysis, however, is poorly studied. Here, we present a computational method, named model-based analysis of alternative polyadenylation using 3’ end-linked reads (MAAPER), to examine APA using nearSite reads. MAAPER uses a probabilistic model to predict PASs for nearSite reads with high accuracy and sensitivity, and examines different types of APA events, including those in 3’UTRs and introns, with robust statistics. We show usability of MAAPER with data from bulk RNA and single cell samples. Our result also highlights the importance of using well annotated PASs for nearSite read analysis.
Project description:Alternative polyadenylation (APA) refers to the regulated selection of polyadenylation sites (PASs) in transcripts, which affects the length of their 3’ untranslated regions (3’UTRs). APA regulates stage- and tissue-specific gene expression by affecting the stability, subcellular localization or translation rate of transcripts. We have recently shown that SRSF3 and SRSF7, two closely related SR proteins, link APA to mRNA export. However, the underlying mechanism for APA regulation by SRSF3 and SRSF7 remained unknown. Here, we combined iCLIP and 3’-end sequencing to find that both proteins bind upstream of proximal PAS (pPAS), but exert opposing effects on 3’UTR length. We show that SRSF7 enhances pPAS usage in a splicing-independent and concentration-dependent manner by recruiting the cleavage factor FIP1, thereby generating short 3’UTRs. SRSF7-specific domains that are absent in SRSF3 are necessary and sufficient for FIP1 recruitment. SRSF3 promotes long 3’UTRs by maintaining high levels of the cleavage factor Im (CFIm) via alternative splicing. Using iCLIP, we show that CFIm binds before and after the pPASs of SRSF3 targets, which masks them and inhibits polyadenylation. In the absence of SRSF3, CFIm levels are strongly reduced, which exposes the pPASs and leads to shorter 3’UTRs. Conversely, during cellular differentiation, 3’UTRs are massively extended, while the levels of SRSF7 and FIP1 strongly decline. Altogether, our data suggest that SRSF7 acts as a sequence-specific enhancer of pPASs, while SRSF3 inhibits pPAS usage by controlling CFIm levels. Our data shed light on a long-standing puzzle of how one factor (CFIm) can inhibit and enhance PAS usage.
Project description:Alternative cleavage and polyadenylation (APA) results in mRNA isoforms containing different 3’ untranslated regions (3’UTRs) and/or coding sequences. How core cleavage and polyadenylation (C/P) factors regulate APA is not well understood. Using siRNA knockdown coupled with deep sequencing, we found that several C/P factors can play significant roles in 3’UTR-APA. Whereas Pcf11 and Fip1 enhance usage of proximal poly(A) sites (pAs), CFI-25/68, PABPN1, and PABPC1 promote usage of distal pAs. Strong cis element biases were found for pAs regulated by CFI or Fip1, and the distance between pAs plays an important role in APA regulation. In addition, intronic pAs are substantially regulated by splicing factors, with U1 mostly influencing C/P events in 5’ introns and U2 impacting those in efficiently spliced introns. Furthermore, PABPN1 regulates expression of transcripts with pAs near the transcription start site, a property possibly related to its role in RNA degradation. Finally, we found that groups of APA events regulated by C/P factors are also modulated in cell differentiation and development with distinct trends. Together, our results indicate that the abundance of different C/P factors and splicing factors plays diverse roles in APA, and is relevant to APA regulation in biological conditions. knockdown experiments of 23 C/P factors, 3 splicing factors and U1D in mouse C2C12 myoblast cells
Project description:Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease with limited effective treatment options, potentiating the importance of uncovering novel drug targets. Here, we target Cleavage and Polyadenylation Specificity Factor 3 (CPSF3), the 3’ endonuclease that catalyzes mRNA cleavage during polyadenylation and histone mRNA processing. We find that CPSF3 is highly expressed in PDAC and is associated with poor prognosis. CPSF3 knockdown blocks PDAC cell proliferation and colony formation in vitro and tumor growth in vivo. Chemical inhibition of CPSF3 by the small molecule JTE-607 also attenuates PDAC cell proliferation and colony formation, while it has no effect on cell proliferation of non-transformed immortalized control pancreatic cells. Mechanistically, JTE-607 induces transcriptional read-through in replication-dependent histones, reduces core histone expression, destabilizes chromatin structure and arrests cells in the S-phase of the cell cycle. Therefore, CPSF3 represents a potential therapeutic target for the treatment of PDAC.
Project description:Alternative cleavage and polyadenylation (APA) results in mRNA isoforms containing different 3’ untranslated regions (3’UTRs) and/or coding sequences. How core cleavage and polyadenylation (C/P) factors regulate APA is not well understood. Using siRNA knockdown coupled with deep sequencing, we found that several C/P factors can play significant roles in 3’UTR-APA. Whereas Pcf11 and Fip1 enhance usage of proximal poly(A) sites (pAs), CFI-25/68, PABPN1, and PABPC1 promote usage of distal pAs. Strong cis element biases were found for pAs regulated by CFI or Fip1, and the distance between pAs plays an important role in APA regulation. In addition, intronic pAs are substantially regulated by splicing factors, with U1 mostly influencing C/P events in 5’ introns and U2 impacting those in efficiently spliced introns. Furthermore, PABPN1 regulates expression of transcripts with pAs near the transcription start site, a property possibly related to its role in RNA degradation. Finally, we found that groups of APA events regulated by C/P factors are also modulated in cell differentiation and development with distinct trends. Together, our results indicate that the abundance of different C/P factors and splicing factors plays diverse roles in APA, and is relevant to APA regulation in biological conditions.
Project description:Alternative polyadenylation (APA) refers to the regulated selection of polyadenylation sites (PASs) in transcripts, which determines the length of their 3’ untranslated regions (3’UTRs). APA regulates stage- and tissue-specific gene expression by affecting the stability, subcellular localization and translation rate of transcripts. We have recently shown that SRSF3 and SRSF7, two closely related SR proteins, connect APA with mRNA export. The mechanism underlying APA regulation by SRSF3 and SRSF7 remained, however, unknown. Here, we combined iCLIP, RNA-Seq and 3’-end sequencing to find that both proteins bind upstream of proximal PASs (pPASs), yet they exert opposite effects on 3’UTR length. We show that SRSF7 enhances pPAS usage in a concentration-dependent but splicing-independent manner by recruiting the cleavage factor FIP1, thereby generating short 3’UTRs. Protein domains unique to SRSF7, which are absent from SRSF3, and hypo-phosphorylation contribute to FIP1 recruitment. In contrast, SRSF3 promotes distal PAS (dPAS) usage and hence long 3’UTRs by maintaining high levels of cleavage factor Im (CFIm) via alternative splicing. Upon reduced expression of SRSF3, CFIm levels strongly decrease and 3’UTRs are globally shortened. In SRSF3-regulated transcripts, CFIm and FIP1 bind upstream of dPASs and promote their usage. Surprisingly, both factors are also recruited to pPASs under conditions where their usage is blocked, suggesting the formation of inactive cleavage complexes. Thus, we identify SRSF3 as a novel regulator of CFIm activity, provide evidence that CFIm inhibits pPAS usage and show that small differences in the domain architecture of SR proteins confer opposite effects on PAS selection.
Project description:Alternative polyadenylation (APA) refers to the regulated selection of polyadenylation sites (PASs) in transcripts, which determines the length of their 3’ untranslated regions (3’UTRs). APA regulates stage- and tissue-specific gene expression by affecting the stability, subcellular localization and translation rate of transcripts. We have recently shown that SRSF3 and SRSF7, two closely related SR proteins, connect APA with mRNA export. The mechanism underlying APA regulation by SRSF3 and SRSF7 remained, however, unknown. Here, we combined iCLIP, RNA-Seq and 3’-end sequencing to find that both proteins bind upstream of proximal PASs (pPASs), yet they exert opposite effects on 3’UTR length. We show that SRSF7 enhances pPAS usage in a concentration-dependent but splicing-independent manner by recruiting the cleavage factor FIP1, thereby generating short 3’UTRs. Protein domains unique to SRSF7, which are absent from SRSF3, and hypo-phosphorylation contribute to FIP1 recruitment. In contrast, SRSF3 promotes distal PAS (dPAS) usage and hence long 3’UTRs by maintaining high levels of cleavage factor Im (CFIm) via alternative splicing. Upon reduced expression of SRSF3, CFIm levels strongly decrease and 3’UTRs are globally shortened. In SRSF3-regulated transcripts, CFIm and FIP1 bind upstream of dPASs and promote their usage. Surprisingly, both factors are also recruited to pPASs under conditions where their usage is blocked, suggesting the formation of inactive cleavage complexes. Thus, we identify SRSF3 as a novel regulator of CFIm activity, provide evidence that CFIm inhibits pPAS usage and show that small differences in the domain architecture of SR proteins confer opposite effects on PAS selection.