Functional interaction of BRCA1-associated BARD1 with polyadenylation factor CstF-50

Polyadenylation of messenger RNA precursors requires a complex protein mach inery that is closely integrated with the even more complex transcriptional apparatus. Here a polyadenylation factor, CstF-50 (cleavage stimulation fa ctor), is shown to interact in vitro and in intact cells with a nuclear pro tein of previously unknown function, BRCA1-associated RING domain protein ( BARD1). The BARD1-CstF-50 interaction inhibits polyadenylation in vitro. BA RD1, like CstF-50, also interacts with RNA polymerase II. These results ind icate that BARD1-mediated inhibition of polyadenylation may prevent inappro priate RNA processing during transcription, perhaps at sites of DNA repair, and they reveal an unanticipated integration of diverse nuclear events.