Sequence and functional analysis of a 7.2 kb DNA fragment containing four open reading frames located between RPB5 and CDC28 on the right arm of chromosome II.

In a coordinated approach, several laboratories sequenced Saccharomyces cerevisiae chromosome II during the European BRIDGE project. Here we report on the sequence and functional analysis of a 7217 bp fragment located on the right arm of chromosome II between RPB5 and CDC28. The fragment contains four open reading frames probably encoding proteins of 79.2 kDa (corresponding gene YBR156c), 12.1 kDa (YBR157c), 62.7 kDa (YBR158w) and 38.7 kDa (YBR159w). All four open reading frames encode new proteins, as concluded from data base searches. The respective genes were destroyed by gene replacement in one allele of diploid cells. After sporulation and tetrad analysis, the resulting mutant haploid strains were investigated. No phenotype with respect to spore germination, viability, carbohydrate utilization, and growth was found for YBR157c, encoding the smallest open reading frame investigated. Gene replacement within the YBR156c gene encoding a highly basic and possibly nuclear located protein was lethal. Ybr158 revealed similarities to the Grrl (Cat80) protein with respect to the leucine-rich region. Cells harboring a mutation in the YBR158w gene showed strongly reduced growth as compared to the wild-type cells. The protein predicted from YBR159w shared 33% identical amino acid residues with the human estradiol 17-beta-hydroxysterol dehydrogenase 3. Haploid ybr159c mutants were only able to grow at reduced temperatures, but even under these conditions the mutants grew slower than wild-type strains.