SWH1 from yeast encodes a candidate nuclear factor containing ankyrin repeats and showing homology to mammalian oxysterol-binding protein.

The isolation of a gene from Saccharomyces cerevisiae, SWH1, with a coding capacity for a 135 kDa protein is reported. The deduced amino acid sequence is homologous to mammalian oxysterol-binding protein (33.6% identical residues at homologous positions) but, in addition, predicts several structural modules that are not present in the mammalian counterpart. These comprise two ankyrin repeats as an N-terminal extension, and highly acidic clusters, poly-asparagine tracts as well as domains that constitute presumptive nuclear targeting signals interspersed in the N-terminal half of the yeast protein. The gene is transcribed constitutively at a low level from a promoter lacking an obvious TATA element. Heterozygous chromosomal deletion of the gene in a diploid yeast strain has no effect on sporulation or on germination of the four spores from one tetrad nor do haploid deletion mutants display any obvious disadvantage regarding growth behaviour or mating.