Cleavage and polyadenylation specific factor 4 promotes colon cancer progression by transcriptionally activating hTERT

Modulation of diverse biological processes by CPSF, the master regulator of mRNA 3' ends

The cleavage and polyadenylation specificity factor (CPSF) complex plays a central role in the formation of mRNA 3' ends, being responsible for the recognition of the poly(A) signal sequence, the endonucleolytic cleavage step, and recruitment of poly(A) polymerase. CPSF has been extensively studied for over three decades, and its functions and those of its individual subunits are becoming increasingly well-defined, with much current research focusing on the impact of these proteins on the normal functioning or disease/stress states of cells. In this review, we provide an overview of the general functions of CPSF and its subunits, followed by a discussion of how they exert their functions in a surprisingly diverse variety of biological processes and cellular conditions. These include transcription termination, small RNA processing, and R-loop prevention/resolution, as well as more generally cancer, differentiation/development, and infection/immunity.

Knockdown of CPSF4 Inhibits Bladder Cancer Cell Growth by Upregulating NRF1

Increasing studies have shown that nuclear respiratory factor 1 (NRF1) deficiency frequently occurs in many human diseases, and its activation can protect neurons and other cells from degenerative diseases and malignant tumors. However, how NRF1 is regulated in bladder cancer remains unknown. Our research aims to reveal the role of leavage and polyadenylation-specific factor 4 (CPSF4) on the growth inhibition effect of bladder cancer and clarify its relationship with NRF1. Here, cell proliferation assay, transwell migration assay and multicellular tumor spheroids (MCTS) formation assay in the bladder cancer cell lines were carried out to measure tumor cell growth. Western bolt assay was carried out to identify the relationship between NRF1 and CPSF4. Also, subcutaneous xenograft tumors in nude mice were established to further validate the inhibition effect of CPSF4 on bladder tumor and the regulation on NRF1. The results in vitro showed that knockdown of CPSF4 strongly reduced the proliferation and migration, and inhibited MCTS formation in 5637 and HT1376 cell lines, while an additional knockdown of increased NRF1 induced by CPSF4 knockdown partially abolished these effects. The results in vivo showed that knockdown of CPSF4 strongly reduced the volume and weight of subcutaneous tumor, and decreased the expression of Ki-67 in tumor tissue, while NRF1 knockdown partially reversed these effects induced by CPSF4 knockdown. Western bolt assay demonstrated that CPSF4 could negatively regulate NRF1. Our results indicated that knock-down of CPSF4 inhibited bladder cancer cell growth by upregulating NRF1, which might provide evidence of CPSF4 as a therapeutic target for bladder cancer.

Cleavage and Polyadenylation-Specific Factor 4 (CPSF4) Expression Is Associated with Enhanced Prostate Cancer Cell Migration and Cell Cycle Dysregulation, In Vitro

Potential oncogene cleavage and polyadenylation specific factor 4 (CPSF4) has been linked to several cancer types. However, little research has been conducted on its function in prostate cancer (PCa). In benign, incidental, advanced, and castrate resistant PCa (CRPCa) patient samples, protein expression of CPSF4 was examined on tissue microarray (TMAs) of 353 PCa patients using immunohistochemistry. Using the 'The Cancer Genome Atlas' Prostate Adenocarcinoma (TCGA PRAD) database, significant correlations were found between high CPSF4 expression and high-risk genomic abnormalities such as ERG-fusion, ETV1-fusion, and SPOP mutations. Gene Set Enrichment Analysis (GSEA) of CPSF4 revealed evidence for the increase in biological processes such as cellular proliferation and metastasis. We further examined the function of CPSF4 in vitro and confirmed CPSF4 clinical outcomes and its underlying mechanism. Our findings showed a substantial correlation between Gleason groups and CPSF4 protein expression. In vitro, CPSF4 knockdown reduced cell invasion and migration while also causing G1 and G2 arrest in PC3 cell lines. Our findings demonstrate that CPSF4 may be used as a possible biomarker in PCa and support its oncogenic function in cellular proliferation and metastasis.

CPSF3 Promotes Pre-mRNA Splicing and Prevents CircRNA Cyclization in Hepatocellular Carcinoma

CircRNAs are crucial in tumorigenesis and metastasis, and are comprehensively downregulated in hepatocellular carcinoma (HCC). Previous studies demonstrated that the back-splicing of circRNAs was closely related to 3'-end splicing. As a core executor of 3'-end cleavage, we hypothesized that CPSF3 modulated circRNA circularization. Clinical data were analyzed to establish the prognostic correlations. Cytological experiments were performed to determine the role of CPSF3 in HCC. A fluorescent reporter was employed to explore the back-splicing mechanism. The circRNAs regulated by CPSF3 were screened by RNA-seq and validated by PCR, and changes in downstream pathways were explored by molecular experiments. Finally, the safety and efficacy of the CPSF3 inhibitor JTE-607 were verified both in vitro and in vivo. The results showed that CPSF3 was highly expressed in HCC cells, promoting their proliferation and migration, and that a high CPSF3 level was predictive of a poor prognosis. A mechanistic study revealed that CPSF3 enhanced RNA cleavage, thereby reducing circRNAs, and increasing linear mRNAs. Furthermore, inhibition of CPSF3 by JET-607 suppressed the proliferation of HCC cells. Our findings indicate that the increase of CPSF3 in HCC promotes the shift of pre-mRNA from circRNA to linear mRNA, leading to uncontrolled cell proliferation. JTE-607 exerted a therapeutic effect on HCC by blocking CPSF3.

CPSF4 promotes tumor-initiating phenotype by enhancing VEGF/NRP2/TAZ signaling in lung cancer

Lung cancer is the leading cause of malignant tumor-related deaths worldwide. The presence of tumor-initiating cells in lung cancer leads to tumor recurrence, metastasis, and resistance to conventional treatment. Cleavage and polyadenylation specificity factor 4 (CPSF4) activation in tumor cells contributes to the poor prognosis of lung cancer. However, the precise biological functions and molecular mechanisms of CPSF4 in the regulation of tumor-initiating cells remain unclear. We demonstrated that CPSF4 promotes tumor-initiating phenotype and confers chemoresistance to paclitaxel both in vitro and in vivo. Mechanistically, we showed that CPSF4 binds to the promoters of vascular endothelial growth factor (VEGF) and neuropilin-2 (NRP2) and activated their transcription. In addition, we showed that CPSF4/VEGF/NRP2-mediated tumor-initiating phenotype and chemoresistance through TAZ induction. Furthermore, analysis of clinical data revealed that lung cancer patients with high CPSF4 expression exhibit high expression levels of VEGF, NRP2, and TAZ and that expression of these proteins are positively correlated with poor prognosis. Importantly, selective inhibition of VEGF, NRP2, or TAZ markedly suppressed CPSF4-mediated tumor-initiating phenotype and chemoresistance. Our findings reveal the mechanism of CPSF4 modulating tumor-initiating phenotype and chemoresistance in lung cancer and indicate that the CPSF4-VEGF-NRP2-TAZ signaling pathway may be a prognosis marker and therapeutic target in lung cancer.

Silencing of CPSF7 inhibits the proliferation, migration, and invasion of lung adenocarcinoma cells by blocking the AKT/mTOR signaling pathway

Cleavage and polyadenylation specific factor 7 (CPSF7) is an important participator in the cleavage and polyadenylation of pre-mRNAs. This study aims to uncover the function and underlying mechanism of CPSF7 in lung adenocarcinoma (LUAD). CPSF7 expression in LUAD cells was measured using real time-quantitative polymerase chain reaction and Western blotting. Our results showed that CPSF7 expression was upregulated in LUAD cell lines (A549, H1299, and HCC827). To explore the function of CPSF7 on LUAD, CPSF7 was silenced by the si-CPSF7 transfection and overexpressed by the oe-CPSF7 transfection in A549 cells. Cell proliferation was measured using cell counting kit-8 and colony formation assays. Cell migration and invasion were measured by wound healing and Transwell assays, respectively. Our data revealed that CPSF7 silencing inhibited the viability, colony formation, migration, and invasion of LUAD cells. On the contrary, CPSF7 overexpression enhanced the malignant characteristics of LUAD cells. Additionally, expression of AKT/mTOR pathway-related proteins was detected using Western blotting. CPSF7 silencing blocked the AKT/mTOR signaling pathway. The intervention of SC79 (an activator of the AKT/mTOR pathway) weakened the antitumor effects of CPSF7 silencing in LUAD cells. Silencing of CPSF7 inhibits the malignant characteristics of LUAD cells by blocking the AKT/mTOR signaling pathway.

CPSF4 regulates circRNA formation and microRNA mediated gene silencing in hepatocellular carcinoma

CircRNAs play essential roles in various physiological processes and involves in many diseases, in particular cancer. Global downregulation of circRNA expression has been observed in hepatocellular carcinoma (HCC) in many studies. Previous studies revealed that the pre-mRNA 3' end processing complex participates in circRNA cyclization and plays an important role in HCC tumorigenesis. Therefore, we explored the role of CPSF4, for 3' end formation and cleavage, in circRNA formation. Clinical research has shown that CPSF4 expression is upregulated in HCC and that high expression of CPSF4 is associated with poor prognosis in HCC patients. Mechanistic studies have demonstrated that CPSF4 reduces the levels of circRNAs, which possess a polyadenylation signal sequence and this decrease in circRNAs reduces the accumulation of miRNA and disrupts the miRNA-mediated gene silencing in HCC. Experiments in cell culture and xenograft mouse models showed that CPSF4 promotes the proliferation of HCC cells and enhances tumorigenicity. Moreover, CPSF4 antagonizes the tumor suppressor effect of its downstream circRNA in HCC. In summary, CPSF4 acts as an oncogene in HCC through circRNA inhibition and disruption of miRNA-mediated gene silencing.

PAPOLA contributes to cyclin D1 mRNA alternative polyadenylation and promotes breast cancer cell proliferation

Poly(A) polymerases add the poly(A) tail at the 3' end of nearly all eukaryotic mRNA, and are associated with proliferation and cancer. To elucidate the role of the most-studied mammalian poly(A) polymerase, poly(A) polymerase α (PAPOLA), in cancer, we assessed its expression in 221 breast cancer samples and found it to correlate strongly with the aggressive triple-negative subtype. Silencing PAPOLA in MCF-7 and MDA-MB-231 breast cancer cells reduced proliferation and anchorage-independent growth by decreasing steady-state cyclin D1 (CCND1) mRNA and protein levels. Whereas the length of the CCND1 mRNA poly(A) tail was not affected, its 3' untranslated region (3'UTR) lengthened. Overexpressing PAPOLA caused CCND1 mRNA 3'UTR shortening with a concomitant increase in the amount of corresponding transcript and protein, resulting in growth arrest in MCF-7 cells and DNA damage in HEK-293 cells. Such overexpression of PAPOLA promoted proliferation in the p53 mutant MDA-MB-231 cells. Our data suggest that PAPOLA is a possible candidate target for the control of tumor growth that is mostly relevant to triple-negative tumors, a group characterized by PAPOLA overexpression and lack of alternative targeted therapies.

Alternative polyadenylation: methods, mechanism, function, and role in cancer

Occurring in over 60% of human genes, alternative polyadenylation (APA) results in numerous transcripts with differing 3'ends, thus greatly expanding the diversity of mRNAs and of proteins derived from a single gene. As a key molecular mechanism, APA is involved in various gene regulation steps including mRNA maturation, mRNA stability, cellular RNA decay, and protein diversification. APA is frequently dysregulated in cancers leading to changes in oncogenes and tumor suppressor gene expressions. Recent studies have revealed various APA regulatory mechanisms that promote the development and progression of a number of human diseases, including cancer. Here, we provide an overview of four types of APA and their impacts on gene regulation. We focus particularly on the interaction of APA with microRNAs, RNA binding proteins and other related factors, the core pre-mRNA 3'end processing complex, and 3'UTR length change. We also describe next-generation sequencing methods and computational tools for use in poly(A) signal detection and APA repositories and databases. Finally, we summarize the current understanding of APA in cancer and provide our vision for future APA related research.

LncRNA NEAT1 Regulates 5-Fu Sensitivity, Apoptosis and Invasion in Colorectal Cancer Through the MiR-150-5p/CPSF4 Axis

Background

Colorectal cancer (CRC) is one of the most prevalent malignancies in the world. Long non-coding RNA (lncRNA) nuclear enriched abundant transcript 1 (NEAT1) is involved in the development of many cancers. However, its role and mechanism in CRC progression still need further exploration.

Methods

The expression levels of lnc-NEAT1, microRNA-150-5p (miR-150-5p) and cleavage and polyadenylation specific factor 4 (CPSF4) were determined by quantitative real-time PCR (qRT-PCR). The sensitivity of cells to 5-fluorouracil (5-Fu) was measured by 3-(4,5-dimethyl-2 thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay. Cell apoptosis and invasion were evaluated by flow cytometry and transwell assays, respectively. Western blot (WB) analysis was used to assess the levels of resistance-related proteins and CPSF4 protein. Besides, dual-luciferase reporter assay was used to verify the interactions among lnc-NEAT1, miR-150-5p and CPSF4. Also, mice xenograft models were used to determine the effect of lnc-NEAT1 on CRC tumor growth in vivo.

Results

In CRC, the expression of lnc-NEAT1 was upregulated and miR-150-5p was downregulated, and the expression of both was negatively correlated. Silencing of lnc-NEAT1 promoted the 5-Fu sensitivity, enhanced the apoptosis and suppressed the invasion of CRC cells. MiR-150-5p could be sponged by lnc-NEAT1, and its inhibitors could partially reverse the effect of lnc-NEAT1 silencing on CRC progression. Besides, CPSF4 could be targeted by miR-150-5p, and its overexpression also could invert the effect of lnc-NEAT1 knockdown on CRC progression. Further, CPSF4 expression was regulated by lnc-NEAT1 and miR-150-5p. In addition, interference of lnc-NEAT1 reduced tumor volume and improved the sensitivity of CRC to 5-Fu in vivo.

Conclusion

Lnc-NEAT1 acted as an oncogene in CRC through regulating CPSF4 expression by sponging miR-150-5p. The discovery of lnc-NEAT1/miR-150-5p/CPSF4 axis provided a novel approach for CRC genomic therapy strategy.

Emerging Roles of RNA 3'-end Cleavage and Polyadenylation in Pathogenesis, Diagnosis and Therapy of Human Disorders

A crucial feature of gene expression involves RNA processing to produce 3′ ends through a process termed 3′ end cleavage and polyadenylation (CPA). This ensures the nascent RNA molecule can exit the nucleus and be translated to ultimately give rise to a protein which can execute a function. Further, alternative polyadenylation (APA) can produce distinct transcript isoforms, profoundly expanding the complexity of the transcriptome. CPA is carried out by multi-component protein complexes interacting with multiple RNA motifs and is tightly coupled to transcription, other steps of RNA processing, and even epigenetic modifications. CPA and APA contribute to the maintenance of a multitude of diverse physiological processes. It is therefore not surprising that disruptions of CPA and APA can lead to devastating disorders. Here, we review potential CPA and APA mechanisms involving both loss and gain of function that can have tremendous impacts on health and disease. Ultimately we highlight the emerging diagnostic and therapeutic potential CPA and APA offer.

Chromosomal Density of Cancer Up-Regulated Genes, Aberrant Enhancer Activity and Cancer Fitness Genes Are Associated with Transcriptional Cis-Effects of Broad Copy Number Gains in Colorectal Cancer

Broad Copy Number Gains (BCNGs) are copy-number increases of chromosomes or large segments of chromosomal arms. Publicly-available single-nucleotide polymorphism (SNP) array and RNA-Seq data of colon adenocarcinoma (COAD) samples from The Cancer Genome Atlas (TCGA) consortium allowed us to design better control groups in order to identify changes in expression due to highly recurrent BCNGs (in chromosomes 20, 8, 7, 13). We identified: (1) Overexpressed Transcripts (OverT), transcripts whose expression increases in "COAD groups bearing a specific BCNG" in comparison to "control COAD groups" not bearing it, and (2) up-regulated/down-regulated transcripts, transcripts whose expression increases/decreases in COAD groups in comparison to normal colon tissue. An analysis of gene expression reveals a correlation between the density of up-regulated genes per selected chromosome and the recurrence rate of their BCNGs. We report an enrichment of gained enhancer activity and of cancer fitness genes among OverT genes. These results support the hypothesis that the chromosomal density of overexpressed cancer fitness genes might play a significant role in the selection of gained chromosomes during cancer evolution. Analysis of functional pathways associated with OverT suggest that some multi-subunit protein complexes (eIF2, eIF3, CSTF and CPSF) are candidate targets for silencing transcriptional therapy.