ISOLATION AND CHARACTERIZATION OF CDNA-ENCODING MOUSE RNA-POLYMERASE-II SUBUNIT RPB14

By means of the yeast two-hybrid system using the 40-kDa subunit of mo use RNA polymerase I, mRPA40, as the bait, we isolated a mouse cDNA wh ich encoded a protein with significant homology in amino acid sequence to the 12.5-kDa subunit of Saccharomyces cerevisiae RNA polymerase II , B12.5 (RPB11). Specific antibody raised against the recombinant prot ein that was derived from the cDNA reacted with a 14-kDa polypeptide i n highly purified mammalian RNA polymerase II and did not react with a ny subunit of RNA polymerase I or III. Moreover, the antibody co-immun oprecipitated the largest subunit of mouse RNA polymerase II. These re sults provide biochemical evidence that the cDNA isolated, named mRPB1 4, encodes a specific subunit of RNA polymerase II, and indicate that the subunit organization of the enzyme is conserved between yeast and mouse. A possible role of the alpha-motif [Dequard-Chablat, M., Riva, M., Caries, C. and Sentenac, A., J. Biol. Chem. 266 (1991) 15300-15307 ] in the protein-protein interaction between mRPA40 and mRPB14 is also discussed.