RQH(1-RELATED TO THE BLOOMS-SYNDROME AND WERNERS-SYNDROME GENES, IS REQUIRED FOR REVERSIBLE S PHASE ARREST(), A FISSION YEAST GENE)

In eukaryotic cells, S phase can be reversibly arrested by drugs that inhibit DNA synthesis or DNA damage, Here we show that recovery from s uch treatments is under genetic control and is defective in fission ye ast rqh1 mutants, rqh1(+), previously known as hus2(+), encodes a puta tive DNA helicase related to the Escherichia coli RecQ helicase, with particular homology to the gene products of the human BLM and WRN gene s and the Saccharomyces cerevisiae SGS1 gene, BLM and WRN are mutated in patients with Bloom's syndrome and Werner's syndrome respectively, Both syndromes are associated with genomic instability and cancer susc eptibility, We show that, like BLM and SGS1, rqh1(+) is required to pr event recombination and that in fission yeast suppression of inappropr iate recombination is essential for reversible S phase arrest.