| Here we describe the function of a U2AF35 related protein ( Urp ) , which is the human homologue of a mouse imprinted gene . ^^^ U2AF35 could not replace Urp in complementation , indicating that their functions do not overlap . ^^^ Co immunodepletion showed that Urp is associated with the U2AF65 / U2AF35 heterodimer . ^^^ Binding studies revealed that Urp specifically interacts with U2AF65 through a U2AF35 homologous region and with SR proteins ( a large family of RS domain containing proteins ) through its RS domain . ^^^ Therefore , Urp and U2AF35 may independently position RS domain containing factors within spliceosomes . . ^^^ |