A new Saccharomyces cerevisiae ankyrin repeat-encoding gene required for a normal rate of cell proliferation

We have characterized a new ankyrin (ANK) repeat-containing Saccharomyces cerevisiae gene, YAR1, located between the HSP82 and SUI3 genes on chromosome XVI. YAR1 encodes a 200-amino-acid (aa) protein with two ANK repeat motifs and an acidic C terminus rich in PEST-like sequences. The Yar1 ANK repeats are most similar to the conserved ANK repeats in the yeast cell cycle transcription factor, Swi6. We show that YAR1 is transcribed as an 800-nucleotide (nt) poly(A)+ mRNA from a promoter lacking a consensus TATA sequence. YAR1 is transcribed in both haploid and diploid cells, and in haploid cells arrested in G1 with alpha-factor or in S phase with hydroxyurea. YAR1 shares an intergenic region with HSP82, and while HSP82 transcription is induced 15-fold by heat shock, transcription of YAR1 is transiently repressed by heat shock. We show that YAR1 is not an essential gene, but that haploid cells bearing a yar1 deletion grow significantly more slowly than do isogenic wild-type cells, especially at low temperature.