Drosophila Sex‐lethal protein mediates polyadenylation switching in the female germline

The Drosophila master sex‐switch protein Sex‐lethal (SXL) regulates the splicing and/or translation of three known targets to mediate somatic sexual differentiation. Genetic studies suggest that additional target(s) of SXL exist, particularly in the female germline. Surprisingly, our detailed molecular characterization of a new potential target of SXL, enhancer of rudimentary ( e ( r )), reveals that SXL regulates e(r) by a novel mechanism—polyadenylation switching—specifically in the female germline. SXL binds to multiple SXL‐binding sites, which include the GU‐rich poly(A) enhancer, and competes for the binding of CstF64 in vitro . The SXL‐binding sites are able to confer sex‐specific poly(A) switching onto an otherwise nonresponsive polyadenylation signal in vivo . The sex‐specific poly(A) switching of e(r) provides a means for translational regulation in germ cells. We present a model for the SXL‐dependent poly(A) site choice in the female germline.