SEQUENCE AND FUNCTIONAL-ANALYSIS OF A 7-CENTER-DOT-2 KB DNA FRAGMENT CONTAINING 4 OPEN READING FRAMES LOCATED BETWEEN RPB5 AND CDC28 ON THERIGHT ARM OF CHROMOSOME-II

In a coordinated approach, several laboratories sequenced Saccharomyce s 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 ge nes were destroyed by gene replacement in one allele of diploid cells. After sporulation and tetrad analysis, the resulting mutant haploid s trains were investigated. No phenotype with respect to spore germinati on, viability, carbohydrate utilization, and growth was found for YBR1 57c, encoding the smallest open reading frame investigated. Gene repla cement within the YBR156c gene encoding a highly basic and possibly nu clear located protein was lethal. Ybr158 revealed similarities to the Grr1 (Cat80) protein with respect to the leucine-rich region. Cells ha rboring 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. The DNA sequence was d eposited at the EMBL data base with accession numbers Z36025 (YBR156c) , Z36026 (YBR157c), Z36027 (YBR158w) and Z36028 (YBR159w).