Student’s ((UBE2C(((((and with DHT treatment in LNCaP cells (Supplementary Figure S5). the downstream signals are considered as the key drivers for CRPC progression 5, 6. Accumulating evidences demonstrate that CRPC remains dependent on NIC3 persistent AR signaling, which is driven by increased androgen synthesis, enhanced nuclear transport of AR, activated enhancer, amplification, overexpression of AR co-regulators, and generation of AR-Vs 5, 7-10. It has been considered that aberrant expression of AR-FL/AR-Vs co-regulators lead to prostate cancer as well as CRPC via the abnormal function of co-regulators on modulation of AR transcriptional network 11-14. AR-V7 is, to date, considered to be the putative AR variant. Importantly, AR-V7 is rarely expressed in primary prostate cancer, but the expression of AR-V7 is increased in CRPC, serving as an independent predictive factor for CRPC development and cancer specific survival 15-17. AR-V7 generation has generally been attributed to alternative splicing of pre-mRNA and/or genomic structural rearrangement 3, 4, 18, 19. Thus, to clarify the mechanisms involved AR-V7 generation as well as AR-FL/AR-V7 co-regulators would be crucial for understanding prostate cancer and the process of CRPC transformation. In eukaryotic cells, mature messenger RNAs are formed by splicing from nascent precursor messenger RNAs, which NIC3 is operated by spliceosomes 6. Spliceosomal proteins can be aberrant expressed or somatic mutated in many cancers, and play vital roles in cancer development and progression 20-22. Pre-mRNA processing factor 6 (PRPF6) is a component of spliceosome, and plays a role in the formation of spliceosome 23. The study concerning the function of PRPF6 in tumor is rarely reported. It has been demonstrated that PRPF6 drives cancer proliferation by preferential splicing of genes associated with cell growth in colorectal carcinoma 24. In addition to the function of PRPF6 on splicing, our study has previously demonstrated that PRPF6 interacts with the N-terminus of AR and enhances AR-mediated transactivation 25. However, little work has been done to understand the molecular mechanism underlying the modulation function of PRPF6 on AR action and the role of PRPF6 in prostate cancer. Here, our results have demonstrated PRPF6 acts as a key regulator for action of both AR-FL and AR-V7, thereby participating in the enhancement of AR-FL NIC3 and AR-V7-induced transactivation in prostate cancer. In addition, PRPF6 is recruited to tumor growth analysis in a mouse xenograft model with CWR22Rv1 cells. Results showed that PRPF6 knockdown reduced tumor burden, with smaller volumes and slower growth rate of the xenograft tumors (Figure ?(Figure1F1F and ?and1G).1G). In line with the tumor growth curve, the tumor NIC3 weights of cells with PRPF6 knockdown were significantly lower (Figure ?(Figure1H).1H). Consistent with the AR-related growth promoting function of PRPF6, xenograft tumors derived by PRPF6 knockdown cells exhibited a significant reduction in prostate-specific antigen (PSA) and ubiquitin-conjugating enzyme E2 C (UBE2C) levels, which are target genes of AR (Figure ?(Figure1I).1I). Taken together, the above results indicated that PRPF6 promotes cell proliferation of prostate cancer cells and AR-FLin CWR22Rv1 cells. Cells were infected with shPRPF6 or shCtrl. After treatment of 10-8 M DHT or ethanol vehicle for 24 hrs, cells were collected for RNA extraction and quantitative real-time PCR were performed. Student’s ((UBE2C(((((and with DHT treatment in LNCaP cells (Supplementary Figure S5). Meanwhile, we analyzed the impact of PRPF6 knockdown in CWR22Rv1 cells, and found expressions of the 10 genes were all repressed both with and LW-1 antibody without DHT treatment (Figure ?(Figure3F).3F). Interestingly, PRPF6 knockdown suppressed expression of (Supplementary Figure S5 and Figure ?Figure3F).3F). Moreover, western blot analysis of the endogenous protein expression in LNCaP cells confirmed that knockdown of PRPF6 led to obvious reductions of PSA protein levels under DHT treatment, while repressed FASN and UBE2C protein expressions both with and without DHT treatment (Figure ?(Figure3G).3G). In CWR22Rv1 cells, PSA, FASN and UBE2C protein expressions were downregulated by PRPF6 knockdown in the absence or presence of DHT, respectively (Figure ?(Figure3G).3G). Taken together, these data suggested that PRPF6, as a cofactor, is required for endogenous AR-regulated gene activation. PRPF6 associates with JMJD1A to enhance AR-induced transactivation We next investigated molecular mechanisms underlying the modulation of PRPF6 on AR-mediated transcription. AR binds to cognate AR-responsive elements (AREs) on its target genes to induce target gene transcription upon the treatment of androgen. We thus turn to examine the recruitment of PRPF6 or AR on the gene (Figure ?(Figure4A).4A). A growing body of evidence support that coordination of pre-mRNA splicing with chromatin remodeling events are involved in transcriptional regulation 27-29, we then ask whether PRPF6 would influence some epigenetic events, including histone modification. Histone H3K4me and H3K36me are hallmarks of.