The Saccharomyces cerevisiae MEC1 gene, which encodes a homolog of the human ATM gene product, is required for G₁ arrest following radiation treatment

The Saccharomyces cerevisiae gene MEC1 represents a structural homolog of the human gene ATM mutated in ataxia telangiectasia patients. Like human ataxia telangiectasia cell lines, mec1 mutants are defective in G₂ and S- phase cell cycle checkpoints in response to radiation treatment. Here we show an additional defect in G₁ arrest following treatment with UV light or gamma rays and map a defective arrest stage at or upstream of START in the yeast cell cycle.