And Uv Light Resistance Phenotypes Haiying Hang, Sarah J. Rauth and Howard B. Lieberman Schizosaccharomyces pombe rad9 mutations can render cells extremely sensitive to the DNA replication inhibitor hydroxyurea, gamma-rays and UV light, and eliminate the associated checkpoint controls. The gene is highly conserved throughout evolution, and homologues exist in Schizosaccharomyces octosporus, Mus musculus and Homo sapiens . S1 through S9 show sites containing amino acids that are evolutionarily conserved or have other potentially important features, and that have been targeted for mutagenesis.
Underlines indicate amino acids within each site that have been altered.
Most of these targeted regions were changed to alanines, whereas rad9-S3 encodes a protein devoid of 22 amino acids normally present in the yeast but absent from the mammalian proteins. Two of the rad9 mutant alleles were fully active, whereas five others completely or partially lost all functions tested. Hydroxyurea-induced checkpoint control could not be uncoupled from drug resistance. These findings are summarized in Table 1. These results establish unique as well as overlapping functional domains within rad9p and provide evidence that the requirements of the protein for promoting resistance to gamma-rays, UV light and hydroxyurea differ.