Functional Characterization of ABC10α, an Essential Polypeptide Shared by All Three Forms of Eukaryotic DNA-dependent RNA Polymerases

Liudmilla Rubbi, Sylvie Labarre-Mariotte, Stéphane Chédin, Pierre Thuriaux
1999 Journal of Biological Chemistry  
ABC10␣ is a small polypeptide shared by the three yeast RNA polymerases. Homologous polypeptides in higher eukaryotes have a zinc-binding CX 2 C . . . CX 2 C motif and a conserved basic C-terminal end. These features are also found in archaeal gene products that may encode an RNA polymerase subunit. The CX 2 C . . . CX 2 C motif is partly dispensable, since only its first cysteine is essential for growth, whereas the basic C-terminal end is critical in vivo. A mutant in the latter domain has an
more » ... RNA polymerase III-specific defect and, in vitro, impairs RNA polymerase III assembly. Polymerase activity was, however, not affected in various faithful transcription assays. The mutant is suppressed by a high gene dosage of the second largest subunit of RNA polymerase III, whereas the homologous subunits of RNA polymerase I and II have aggravating effects. In a two-hybrid assay, ABC10␣ binds to the C-terminal half of the second largest subunit of RNA polymerase I, in a way that requires the integrity of the CX 2 C . . . CX 2 C motif. Thus, ABC10␣ appears to interact directly with the second largest subunit during polymerase assembly. This interaction is presumably a major rate-limiting step in assembly, since diploid cells containing only one functional gene copy for ABC10␣ have a partial growth defect.
doi:10.1074/jbc.274.44.31485 pmid:10531351 fatcat:nkeq6rtx2fe3bngo6gh2re4mn4