PROTEIN-INTERACTION CLONING IN YEAST OF THE MOUSE 3RD LARGEST RNA-POLYMERASE-II SUBUNIT, MRPB31

The cDNA encoding a protein that interacts with the mouse homologue of the yeast RNA polymerase II (polII) subunit, RPB11, and the human pol II subunit, hRPB14, has been isolated by protein interaction cloning. Its deduced amino acid sequence has 96% homology to the human third la rgest polII subunit, hRPB33 [Pati and Weissman (1990) J. Biol. Chem. 2 65, 8400-8405]. Therefore, we conclude that the cloned cDNA encodes th e mouse third largest polII subunit, mRPB31. Isolation of cDNA by prot ein interaction cloning provides evidence supporting the hypothesis, f irst proposed for human polII assembly [Pati (1994) Gene 145, 289-292] , that the mRPB31/mRPB14 heterodimer, rather than the mRPB31 homodimer , forms in the mouse polII assembly. Indeed, in the yeast two-hybrid s ystem, mRPB31 was shown to fail to form homodimer.