ASingle Ataxia Telangiectasia Genewith a Product Similar toP1-3Kinase

chromosomal instability, cancerpredisposition, radiation sensitivity, andcell cycle abnormalities. Thedisease isgenetically heterogeneous, with four complementation groupsthat havebeensuspected torepresent different genes.ATM,whichhasatranscript of12kilobases, was found tobemutated inATpatients fromall complementation groups,indicating that itisprobably thesole gene responsible forthis disorder. Apartial ATMcomplementary DNAclone of5.9kilobases encoded a putative protein thatissimilar toseveral yeastandmammalian phosphatidylinositol-3' kinases that areinvolved inmitogenic signal transduction, meiotic recombination, andcell cycle control. Thediscovery ofATMshould enhance understanding of ATandrelated syndromes andmay allow theidentification ofATheterozygotes, whoare atincreased risk ofcancer.