title: Pathways of resistance to thymineless death in Escherichia coli and the function of UvrD.
abstract: Thymineless death (TLD) is the rapid loss of viability in bacterial, yeast, and human cells starved of thymine. TLD is the mode of action of common anticancer drugs and some antibiotics. TLD in Escherichia coli is accompanied by blocked replication and chromosomal DNA loss and recent work identified activities of recombination protein RecA and the SOS DNA-damage response as causes of TLD. Here, we examine the basis of hypersensitivity to thymine deprivation (hyper-TLD) in mutants that lack the UvrD helicase, which opposes RecA action and participates in some DNA repair mechanisms, RecBCD exonuclease, which degrades double-stranded linear DNA and works with RecA in double-strand-break repair and SOS induction, and RuvABC Holliday-junction resolvase. We report that hyper-TLD in uvrD cells is partly RecA dependent and cannot be attributed to accumulation of intermediates in mismatch repair or nucleotide-excision repair. These data imply that both its known role in opposing RecA and an additional as-yet-unknown function of UvrD promote TLD resistance. The hyper-TLD of ruvABC cells requires RecA but not RecQ or RecJ. The hyper-TLD of recB cells requires neither RecA nor RecQ, implying that neither recombination nor SOS induction causes hyper-TLD in recB cells, and RecQ is not the sole source of double-strand ends (DSEs) during TLD, as previously proposed; models are suggested. These results define pathways by which cells resist TLD and suggest strategies for combating TLD resistance during chemotherapies.
authors.affiliation: Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030-3411, USA.
authors.forename: Natalie C
authors.initials: NC
authors.lastname: Fonville
authors.forename: Zalman
authors.initials: Z
authors.lastname: Vaksman
authors.forename: Jessica
authors.initials: J
authors.lastname: DeNapoli
authors.forename: P J
authors.initials: PJ
authors.lastname: Hastings
authors.forename: Susan M
authors.initials: SM
authors.lastname: Rosenberg
mesh_terms: D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D004260:DNA Repair; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D005090:Exodeoxyribonucleases / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D053858:Metabolic Networks and Pathways; D045522:Recombinases / Q000378:metabolism; D011995:Recombination, Genetic; D013014:SOS Response, Genetics; D013941:Thymine / Q000378:metabolism*
chemical_list: D029968:Escherichia coli Proteins; D045522:Recombinases; D005090:Exodeoxyribonucleases; C506746:UvrD protein, E coli; D004265:DNA Helicases; D013941:Thymine