PUF60: A novel U2AF65-related splicing activity

We have identified a new pyrimidine-tract binding factor, PUF, that is requ ired, together with U2AF, for efficient reconstitution of RNA splicing in v itro. The activity has been purified and consists of two proteins, PUF60 an d the previously described splicing factor p54. p54 and PUF60 form a stable complex in vitro when cotranslated in a reaction mixture. PUP activity, in conjunction with U2AF, facilitates the association of U2 snRNP with the pr e-mRNA, This reaction is dependent upon the presence of the large subunit o f U2AF, U2AF65, but not the small subunit U2AF35, PUF60 is homologous to bo th U2AF65 and the yeast splicing factor Mud2p, The C-terminal domain of PUF 60, the PUMP domain, is distantly related to the RNA-recognition motif doma in, and is probably important in protein-protein interactions.