Interaction between a complex of RNA polymerase III subunits and the 70-kDa component of transcription factor IIIB.

A system that detects the formation of complexes between different proteins by linking them to separate domains of the GALA transcription activator protein has been used to study protein-protein interactions between four essential and unique subunits of yeast RNA polymerase I11 ((282, C53, C34 and C31), the 70-kDa component of the initiation transcription factor IIIB (TFIIIB70) and the TATA-binding protein.W e found that C82, C34, and C31 are able to combine with each other in uivo and that C34 interacts with TFIIIB70.These results suggest that C34 and TFIIIB70 are specificity determinants of the RNA polymerase 111-TFIIIB interaction.Each of the three eukaryotic RNA polymerases are composed of numerous polypeptides.For example Saccharomyces cerevisiae RNApolymerase I11 (or C) is constituted of many subunits, 13 of which have been well characterized (Sentenac, 1985; Thuriaw and Sentenac, 1992).Its two largest subunits are homologous to the largest subunits of yeast RNA polymerase I and 11, and to bacterial subunits p' and p. TWO other subunits are common to RNA polymerases I and 111, and five small polypeptides a r e shared by all three RNA polymerases.Finally, sub-