PTBP1 Regulates DNMT3B Alternative Splicing by Interacting with RALY to Enhance the Radioresistance of Prostate Cancer
Radiotherapy is a curative arsenal for prostate cancer (PCa), but radioresistance seriously compromises its effectiveness. Dysregulated RNA splicing factors are extensively involved in tumor progression. Nonetheless, the role of splicing factors in radioresistance remains largely unexplored in PCa. Here, we identified 23 splicing factors that are differentially expressed between PCa and adjacent normal tissues across multiple public PCa databases. Among those genes, polypyrimidine tract binding protein 1 (PTBP1) was significantly upregulated in PCa and was positively associated with advanced clinicopathological features and poor prognosis. Gain- and loss-of-function experiments demonstrated that PTBP1 markedly reinforced genomic DNA stability to desensitize PCa cells to irradiation in vitro and in vivo. Mechanistically, PTBP1 interacted with the HnRNP associated with lethal yellow protein homolog (RALY) and regulated exon 5 splicing of methyltransferase 3b (DNMT3B) from DNMT3B-S to DNMT3B-L. Furthermore, upregulation of DNMT3B-L induced promoter methylation of dual-specificity phosphatase-2 (DUSP2) and subsequently inhibited DUSP2 expression, thereby increasing radioresistance in PCa. Our findings highlight the role of splicing factors in inducing aberrant splicing events in response to radiotherapy and the potential role of PTBP1 and DNMT3B-L in reversing radioresistance in PCa. Overall design: Prostate cancer cell line DU145 was transfected with the contol siRNA, PTBP1 siRNA  or DNMT3B-L siRNA for 48h, respectively. The RNA of the treated cells was extracted and sequenced on Illumina HiSeq 2500 platform and 100-bp paired-end reads were generated.