The systematic deletion of all yeast ORFs, the Saccharomyces Genome Deletion Project, provides a powerful resource for large-scale 'parallel deletion analysis'. In the October 23 Proceedings of the National Academy of Sciences, Geoff Birrell and colleagues at Stanford University School of Medicine describe a screen for sensitivity to a genome-damaging agent (Proc Natl Acad Sci USA 2001, 98:12608-12613).

They screened pools of 4,627 deletion strains for killing by ultraviolet (UV) irradiation and used oligonucleotide arrays to follow radiation sensitivity. They identified 25 known UV-sensitive deletions and found three new genes not previously linked with UV sensitivity. Two of these, CaSm and AF9, have human orthologs implicated in cancer, demonstrating how such a powerful approach can provide important insights into the mechanism of cytotoxicity by genotoxic agents.