The TFIIIC90 subunit of TFIIIC interacts with multiple components of the RNA polymerase III machinery and contains a histone-specific acetyltransferase activity

Human transcription factor IIIC (hTFIIIC) is a multisubunit complex that di rectly recognizes promoter elements and recruits TFIIIB and RNA polymerase III. Here we describe the cDNA cloning and characterization of the 90-kDa s ubunit (hTFIIIC90) that is present within a DNA-binding subcomplex (TFIIIC2 ) of TFIIIC. hTFIIIC90 has no specific homology to any of the known yeast T FIIIC subunits. Immunodepletion and immunoprecipitation studies indicate th at hTFIIIC90 is a bona fide subunit of TFIIIC2 and absolutely required for RNA polymerase III transcription. hTFIIIC90 shows interactions with the hTF IIIC220, hTFIIIC110, and hTFIIIC63 subunits of TFIIIC, the hTFIIIB90 subuni t of TFIIIB, and the human RPC39 (hRPC39) and hRPC62 subunits of an initiat ion-specific subcomplex of RNA polymerase III. These interactions may facil itate both TFIIIB and RNA polymerase III recruitment to the preinitiation c omplex by TFIIIC. We show that hTFIIIC90 has an intrinsic histone acetyltra nsferase activity with a substrate specificity for histone H3.