Moreover, ATR, the vertebrate ortholog of Sz. pombeSPRad3, differs in function from SPRad3 because ATM has a major role in the response to double-stranded DNA breaks and because activation of ATM (AtaxiaTelangiectasia-mutated) leads to CHK2 activation (Matsuoka et al. 1998). This evidence concerns the gene ATM and Ataxia-telangiectasia.