CHARACTERIZATION OF A MUTANT STRAIN OF SACCHAROMYCES-CEREVISIAE WITH A DELETION OF THE RAD27 GENE, A STRUCTURAL HOMOLOG OF THE RAD2 NUCLEOTIDE EXCISION-REPAIR GENE

We have constructed a strain of Saccharomyces cerevisiae with a deleti on of the YKL510 open reading frame, which was initially identified in chromosome XI as a homolog of the RAD2 nucleotide excision repair gen e (A. Jacquier, P. Legrain, and B. Dujon, Yeast 8:121-132, 1992). The mutant strain exhibits increased sensitivity to UV light and to the al kylating agent methylmethane sulfonate but not to ionizing radiation. We have renamed the YKL510 open reading frame the RAD27 gene, in keepi ng with the accepted nomenclature for radiation-sensitive yeast mutant s. Epistasis analysis indicates that the gene is in the RAD6 group of genes, which are involved in DNA damage tolerance. The mutant strain a lso exhibits increased plasmid loss, increased spontaneous mutagenesis , and a temperature-sensitive lethality whose phenotype suggests a def ect in DNA replication. Levels of the RAD27 gene transcript are cell c ycle regulated in a manner similar to those for several other genes wh ose products are known to be involved in DNA replication. We discuss t he possible role of Rad27 proteid in DNA repair and replication.