A genome-wide screen in Saccharomyces cerevisiae for genes affecting UV radiation sensitivity.

The recent completion of the deletion of essentially all of the ORFs in yeast is an important new resource for identifying the phenotypes of unknown genes. Each ORF is replaced with a cassette containing unique tag sequences that allow rapid parallel analysis of strains in a pool by using hybridization to a high-density oligonucleotide array. We examined the utility of this system to identify genes conferring resistance to UV irradiation by using a pool of 4,627 individual homozygous deletion strains (representing deletions of all nonessential genes). We identified most of the nonessential genes previously shown to be involved in nucleotide excision repair, in cell cycle checkpoints, in homologous recombination, and in postreplication repair after UV damage. We also identified and individually confirmed, by replacing the genes, three new genes, to our knowledge not previously reported to confer UV sensitivity when deleted. Two of these newly identified genes have human orthologs associated with cancer, demonstrating the potential of this system to uncover human genes affecting sensitivity to DNA-damaging agents and genes potentially involved in cancer formation.

The complete nucleotide sequence of the structural gene TOP2 of yeast DNA topoisomerase II.

The nucleotide sequence of the gene TOP2 encoding DNA topoisomerase II of the yeast Saccharomyces cerevisiae has been determined. The entire coding sequence of the gene lies within an open reading frame, and there are 1429 amino acids in the single polypeptide protein if translation is assumed to start at the first ATG in this frame. The calculated subunit and molecular mass of the enzyme is 164,000 and 328,000 daltons, respectively. The transcriptional starts of the gene and a polyadenylation site of the message have also been mapped.

Tandem regions of yeast DNA topoisomerase II share homology with different subunits of bacterial gyrase.

The nucleotide sequence for the Saccharomyces cerevisiae gene TOP2, which encodes DNA topoisomerase II, was compared with the sequence for bacterial DNA gyrase. The amino and carboxyl terminal halves of the single-subunit yeast enzyme showed homologies with the B and A subunits of bacterial gyrase, respectively, at corresponding positions along the polypeptide chains. Although the two enzymes differ in both quaternary structure and activity, the homology between the two proteins indicates mechanistic as well as structural similarities, and a probable evolutionary relationship.