A CONJUGATION-SPECIFIC GENE (CNJC) FROM TETRAHYMENA ENCODES A PROTEIN HOMOLOGOUS TO YEAST RNA-POLYMERASE SUBUNITS (RPB3, RPC40) AND SIMILAR TO A PORTION OF THE PROKARYOTIC RNA-POLYMERASE ALPHA-SUBUNIT (RPOA)

The cnjC gene from the protozoanTetrahymena thermophila was completely sequenced. The deduced gene product was found to have significant sequence similarity to the yeast and prokaryotic RNA polymerase subunits involved with subunit assembly. Since cnjC is active only during the sexual stage (conjugation) ofTetrahymena's life cycle, these results indicate it may be part of a novel type of transcriptlonal control. The yeast proteins to which theTetrahymenacnjC is homologous are the 40 kd protein of RNA polymerases I and III (coded for by gene RPC40) and the third-largest subunit of RNA polymerase II (coded for by gene RPB3). The degree of similarity of the cnjC protein to the two yeast subunits was found to be greater than the similarity of the two yeast subunits to each other. The a subunit of the core RNA polymerase from prokaryotes (coded for by gene rpoA) was found tohave regions of similarity to the cnjC protein as well as to the subunits encoded by RPC40 and RPB3. Regions of high conservation among the four proteins are noted. The significance of these results is discussed. © 1990 Oxford University Press.