SWH1 FROM YEAST ENCODES A CANDIDATE NUCLEAR FACTOR-CONTAINING ANKYRINREPEATS AND SHOWING HOMOLOGY TO MAMMALIAN OXYSTEROL-BINDING PROTEIN

The isolation of a gene from Saccharomyces cerevisiae, SWH1, with a co ding capacity for a 135 kDa protein is reported. The deduced amino aci d sequence is homologous to mammalian oxysterol-binding protein (33.6% identical residues at homologous positions) but, in addition, predict s several structural modules that are not present in the mammalian cou nterpart. These comprise two ankyrin repeats as an N-terminal extensio n, and highly acidic dusters, poly-asparagine tracts as well as domain s that constitute presumptive nuclear targeting signals interspersed i n the N-terminal half of the yeast protein. The gene is transcribed co nstitutively at a low level from a promoter lacking an obvious TATA el ement. Heterozygous chromosomal deletion of the gene in a diploid yeas t strain has no effect on sporulation or on germination of the four sp ores from one tetrad nor do haploid deletion mutants display any obvio us disadvantage regarding growth behaviour or mating.