Yeast and human genes that affect the Escherichia coli SOS response

The sequencing of the human genome has led to the identification of many genes whose functions remain to be determined. Because of conservation of genetic function, microbial systems have often been used for identification and characterization of human genes. We have investigated the use of the Escherichia coli SOS induction assay as a screen for yeast and human genes that might play a role in DNA metabolism and/or in genome stability. The SOS system has previously been used to analyze bacterial and viral genes that directly modify DNA. An initial screen of meiotically expressed yeast genes revealed several genes associated with chromosome metabolism (e.g., RAD51 and HHT1 as well as others). The SOS induction assay was then extended to the isolation of human genes. Several known human genes involved in DNA metabolism, such as the Ku70 end-binding protein and DNA ligase IV, were identified, as well as a large number of previously unknown genes. Thus, the SOS assay can be used to identify and characterize human genes, many of which may participate in chromosome metabolism.