MOLECULAR CHARACTERIZATION OF THE PEL1 GENE ENCODING A PUTATIVE PHOSPHATIDYLSERINE SYNTHASE

In the yeast Saccharomyces cerevisiae the PEL1 gene is essential for t he viability of rho(-) Irho degrees petite mutants, and its mutation i n respiring cells results in a pleiotropic phenotype. Results of compl ementation analysis with different subclones of chromosomal DNA and re -sequencing of the YCL4w-YCL3w segment of chromosome III demonstrate t hat the coding region of the PEL1 gene corresponds to 1467 bp. The siz e of the PEL1 transcript in Northern blot analysis was estimated to be approximately 1.5 kb. Transcription initiation in wild-type cells was found to occur at the position - 9 relative to the ATG. The PEL1 gene was moderately expressed irrespective of the state of the mitochondri al genome and the nature of the carbon sources. Disruption of the PEL1 gene was not lethal and resulted in the same phenotype as observed wi th the pel1 mutant, i.e. the cells were not able to survive ethidium b romide mutagenesis, were thermosensitive for growth on glucose at 37 d egrees C and failed to grow on minimal glycerol medium. Although the P el1 protein exhibits significant similarity to a family of phosphatidy lserine synthases, the disrupted PEL1 gene was not complemented by the multicopy plasmid-borne CHO1 gene encoding an essential yeast phospha tidylserine synthase. The Accession Number of the PEL1 gene in the EMB L data library is Z48162.