Among the three DMTF1 splicing isoforms, DMTF1α acts as a tumour suppressor through promoting p14ARF expression, while DMTF1β exhibits an oncogenic role likely through antagonizing DMTF1α. However, the molecular mechanism underlying alternative splicing of DMTF1 pre-mRNA has not been delineated. In the current study, we discovered SRSF5 as a regulatory protein binding to a region located between DMTF1β and α acceptor splice sites to promote DMTF1β and γ splicing. We demonstrated that SRSF5 expression positively...