R-loop Resolution by ARIP4 Helicase Promotes Androgen-dependent Transcription Induction
Pausing of RNA Polymerase II (PolII) at transcription start sites (TSSs) primes target genes for productive elongation. Coincidentally, DNA double-strand breaks (DSBs) enrich at highly transcribed and PolII-paused genes, although whether these events may be functionally coupled remains undefined. Using androgen-responsive cancer cells as a model, we identified the ARIP4 helicase as a driver of androgen-dependent transcription induction. ChIP-seq analysis revealed that ARIP4 preferentially occupies promoter proximal regions (TSS) that overlap with paused PolII. Moreover, we found that ARIP4 complexes with TOP2B, and mediates transient DSB formation at TSSs upon hormone stimulation. Accordingly, ARIP4 deficiency compromised release of paused PolII and resulted in R-loop accumulation at a panel of highly-transcribed androgen receptor (AR) target genes. Finally, we showed that ARIP4 binds and unwinds R-loops in vitro, and its expression positively correlates with prostate cancer progression. Together, we propose a model in which androgen stimulation triggers PolII pause release, at least in part via ARIP4-mediated unwinding of R loops, and in effect prevents excessive pausing-associated R-loops that impede loading and progression of subsequent PolII molecules.