KLUYVEROMYCES-LACTIS SEF1 AND ITS SACCHAROMYCES-CEREVISIAE HOMOLOG BYPASS THE UNKNOWN ESSENTIAL FUNCTION, BUT NOT THE MITOCHONDRIAL RNASE-PFUNCTION, OF THE SACCHAROMYCES-CEREVISIAE RPM2 GENE

RPM2 is a Saccharomyces cerevisiae nuclear gene required for normal ce ll growth yet the only known function of Rpm2p is as a protein subunit of yeast mitochondrial RNase P, an enzyme responsible for the 5' matu ration of mitochondrial tRNAs. Since mitochondrial protein synthesis i n S. cerevisiae is not essential for viability, RPM2 must provide anot her function in addition to its known role as a mitochondrial tRNA pro cessing enzyme. During a search for RPM2 homologues from Kluyveromyces lactis, we recovered a K. lactis gene that compensates for the essent ial function but not the RNase P function of RPM2. We have named this gene SEF1 (Suppressor of the Essential Function). DNA sequence analysi s of SEF1 reveals it contains a Zn(2)-Cys(6) binuclear cluster motif f ound in a growing number of yeast transcription factors. The SEF1 homo logue of S. cerevisiae also compensates for the essential function of RPM2. The two proteins share 49% identity and 72% amino acid sequence similarity. The SEF1 sequence has been deposited in the GenBank data l ibrary under accession number U92898. (C) 1998 John Wiley & Sons, Ltd.