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

Integrative analysis of small non-coding RNAs predicts a piRNA/miRNA-CCND1/BRAF/HRH1/ATXN3 regulatory circuit that drives oncogenesis in glioblastoma

The high-grade astrocytoma, glioblastoma multiforme (GBM), is the most common primary tumour of the brain, known for being aggressive and developing drug resistance. The non-coding RNAs (ncRNAs), such as microRNAs (miRNAs) and Piwi-interacting RNAs (piRNAs), have critical functions in tumorigenesis and cancer drug resistance. Hence, we profiled miRNAs, piRNAs, and genes in U-87 MG GBM cells by next-generation sequencing and performed target prediction, pathway enrichment, protein-protein interaction, co-expression studies, and qRT-PCR validations to predict their possible roles in the malignancy. The study identified 335 miRNAs, 665 piRNAs, and 4286 genes differentially expressed (DE) in GBM. Among them 128 DE genes (DEGs) were targeted by both miRNAs and piRNAs, while 1817 and 192 were targeted solely by miRNAs or piRNAs, respectively. Interestingly, all the DEG targets enriched in cancer processes were overexpressed in GBM. Among these, BRAF was solely targeted by two piRNAs and this was found to be co-expressed with 19 sole targets of 5 miRNAs, including CCND1, and both were found to regulate cell proliferation in cancer. We conjectured that upregulated HRH1 and ATXN3 were targeted by both piRNAs and miRNAs, and along with BRAF and CCND1 might induce cell proliferation in GBM through G-protein-coupled receptor or Akt signalling pathways due to downregulation of the respective targeting small RNAs. These targets were also linked to the progression and overall survival of GBM patients, suggesting that they could be used as biomarkers. Overall, this study has identified a few novel ncRNA targets, which might aid in a better understanding of GBM pathogenesis.

Targeting the mRNA endonuclease CPSF73 inhibits breast cancer cell migration, invasion, and self-renewal

Cleavage by the endonuclease CPSF73 and polyadenylation of nascent RNA is an essential step in co-transcriptional mRNA maturation. Recent work has surprisingly identified CPSF73 as a promising drug target for inhibiting the growth of specific cancers, triggering further studies on understanding CPSF73 regulation and functions in cells. Here, we report that a HECT-like E3 ligase, UBE3D, participates in stabilizing CPFS73 protein by preventing its ubiquitin-mediated degradation by the proteasome. Depletion of UBE3D leads to CPSF73 downregulation, a pre-mRNA cleavage defect, and dysregulated gene expression in cells. UBE3D dysfunction or chemical inactivation of CPSF73 inhibited migration and invasion as well as stem cell renewal phenotypes in vitro in triple-negative breast cancer cells. In addition, genetic overexpression of CPSF73 promoted breast cancer stemness and knocking down CPSF73 inhibited stem cell renewal properties. Together, our findings indicate that targeting the pre-mRNA processing nuclease CPSF73 has potential for breast cancer therapy.

Alternative polyadenylation: An enigma of transcript length variation in health and disease

Alternative polyadenylation (APA) is a molecular mechanism during a pre-mRNA processing that involves usage of more than one polyadenylation site (PA-site) generating transcripts of varying length from a single gene. The location of a PA-site affects transcript length and coding potential of an mRNA contributing to both mRNA and protein diversification. This variation in the transcript length affects mRNA stability and translation, mRNA subcellular and tissue localization, and protein function. APA is now considered as an important regulatory mechanism in the pathophysiology of human diseases. An important consequence of the changes in the length of 3'-untranslated region (UTR) from disease-induced APA is altered protein expression. Yet, the relationship between 3'-UTR length and protein expression remains a paradox in a majority of diseases. Here, we review occurrence of APA, mechanism of PA-site selection, and consequences of transcript length variation in different diseases. Emerging evidence reveals coordinated involvement of core RNA processing factors including poly(A) polymerases in the PA-site selection in diseases-associated APAs. Targeting such APA regulators will be therapeutically significant in combating drug resistance in cancer and other complex diseases. This article is categorized under: RNA Processing > 3' End Processing RNA in Disease and Development > RNA in Disease Translation > Regulation.