Androgen signaling connects short isoform production to breakpoint formation at Ewing sarcoma breakpoint region 1 via an R-loop-dependent mechanism

Abstract

Ewing's sarcoma is most prevalent in adolescent males and is almost always the result of a chromosomal rearrangement that creases a fusion gene with EWSR1 as the 5' fusion partner.Why EWSR1 is more commonly rearranged than other, similar genes and why Ewing's sarcoma is predisposed to adolescent males is not known. We found that in prostate cancer, androgen signaling upregulated a 5' EWSR1 isoform by promoting usage of an intronic polyadenylation site proximal to the Ewing's sarcoma breakpoint hotspot. An intronic Androgen Receptor (AR) binding site was necessary for this upregulation. Strikingly, androgen signaling drove high levels of breakpoint formation in EWSR1. Androgen signaling also promoted R-loop formation and Rloops were necessary for breakpoint formation. These data suggest that aberrant androgen signaling leads to R-loop-mediated DNA damage at the EWSR1 breakpoint hotspot and subsequent misrepair could promote EWSR1 gene fusions in Ewing's sarcoma.