FUNCTIONAL ASSOCIATION OF ESSENTIAL SPLICING FACTOR(S) WITH PRP19 IN A PROTEIN COMPLEX

We have previously shown that the yeast PRP19 protein is a spliceosoma l component, but is not tightly associated with small nuclear RNAs. It appears to associate with the spliceosome concomitant with or just af ter dissociation of the U4 small nuclear RNA during spliceosome assemb ly. We have found that PRP19 is associated with a protein complex in t he splicing extract and that at least one of the associated components is essential for splicing. Taking advantage of the epitope tagging te chnique, we have isolated the PRP19-associated complex by affinity chr omatography. The isolated complex is functional for complementation fo r the heat-inactivated prpl9 mutant extract, and consists of at least seven polypeptides in addition to PRP19. At least three of these can i nteract directly with the PRP19 protein. We also show that the PRP19 p rotein itself is in an oligomeric form, which might be a prerequisite for its interaction with these proteins.