THE FIRST MEMBER OF A NOVEL FAMILY OF PRO TEIN FACTORS OF EUKARYOTIC TRANSCRIPTION DISCOVERED BY THE HETEROSPECIFIC COMPLEMENTATION

The cDNA of a previously uncharacterized gene fet5 (factor of eukaryot ic transcription, clone no, 5) of the fission yeast Schizosaccharomyce s pombe was cloned by the heterospecific complementation of a conditio nal mutant of Saccharomyces cerevisiae defective in the function of th e RNA polymerases I-III common subunit ABC10 beta. The gene encodes a new factor of eukaryotic transcription, Fet5, the first member of a su perfamily of proteins for which the area of functioning is determined. The Fet5-superfamily consists of three distinct families of proteins highly evolutionarily conserved and widely spread among eukaryotes. Fe atures of the Fet5 amino acid sequence suggest that it belongs to ATP/ GTP-binding proteins.