Interactome for auxiliary splicing factor U2AF65 suggests diverse roles

U2 small nuclear ribonucleoprotein auxiliary factor (U2AF) is an essential component of the splicing machinery that is composed of two protein subunits, the 35 kDa U2AF35 (U2AF1) and the 65 kDa U2AF65 (U2AF2). U2AF interacts with various splicing factors within this machinery. Here we expand the list of mammalian splicing factors that are known to interact with U2AF65 as well as the list of nuclear proteins not known to participate in splicing that interact with U2AF65. Using a yeast two-hybrid system, we found fourteen U2AF65-interacting proteins. The validity of the screen was confirmed by identification of five known U2AF65-interacting proteins, including its heterodimeric partner, U2AF35. In addition to binding these known partners, we found previously unrecognized U2AF65 interactions with four splicing-related proteins (DDX39, SFRS3, SFRS18, SNRPA), two zinc finger proteins (ZFP809 and ZC3H11A), a U2AF65 homolog (RBM39), and two other regulatory proteins (DAXX and SERBP1). We report which regions of U2AF65 each of these proteins interacts with and we discuss their potential roles in regulation of pre-mRNA splicing, 3′-end mRNA processing, and U2AF65 sub-nuclear localization. These findings suggest expanded roles for U2AF65 in both splicing and non-splicing functions.