TEL1, AN SACCHAROMYCES-CEREVISIAE HOMOLOG OF THE HUMAN GENE MUTATED IN ATAXIA-TELANGIECTASIA, IS FUNCTIONALLY RELATED TO THE YEAST CHECKPOINT GENE MEC1

Patients with the genetic disorder ataxia telangiectasia (AT) have mut ations in the AT mutated (ATM) gene, which is homologous to TEL1 and t he checkpoint gene MEC1. A tel1 deletion mutant, unlike a mec1 deletio n, is viable and does not exhibit increased sensitivity to DNA-damagin g agents. However, increased dosage of TEL1 rescues sensitivity of a m ec1 mutant, mec1-1, to DNA-damaging agents and rescues viability of a mec1 disruption. mec1-1 tel1 Delta 1 double mutants are synergisticall y sensitive to DNA-damaging agents, including radiomimetic drugs. Thes e data indicate that TEL1 and MEC1 are functionally related and that f unctions of the ATM gene are apparently divided between at least two S . cerevisiae homologs.