title: Loss of heterozygosity in yeast can occur by ultraviolet irradiation during the S phase of the cell cycle.
abstract: A CAN1/can1Delta heterozygous allele that determines loss of heterozygosity (LOH) was used to study recombination in Saccharomyces cerevisiae cells exposed to ultraviolet (UV) light at different points in the cell cycle. With this allele, recombination events can be detected as canavanine-resistant mutations after exposure of cells to UV radiation, since a significant fraction of LOH events appear to arise from recombination between homologous chromosomes. The radiation caused a higher level of LOH in cells that were in the S phase of the cell cycle relative to either cells at other points in the cell cycle or unsynchronized cells. In contrast, the inactivation of nucleotide excision repair abolished the cell cycle-specific induction by UV of LOH. We hypothesize that DNA lesions, if not repaired, were converted into double-strand breaks during stalled replication and these breaks could be repaired through recombination using a non-sister chromatid and probably also the sister chromatid. We argue that LOH may be an outcome used by yeast cells to recover from stalled replication at a lesion.
authors.affiliation: Graduate School of Life Sciences, Tohoku University, Sendai 980-8577, Japan.
authors.forename: Yasukazu
authors.initials: Y
authors.lastname: Daigaku
authors.forename: Satsuki
authors.initials: S
authors.lastname: Mashiko
authors.forename: Keiichiro
authors.initials: K
authors.lastname: Mishiba
authors.forename: Saburo
authors.initials: S
authors.lastname: Yamamura
authors.forename: Ayako
authors.initials: A
authors.lastname: Ui
authors.forename: Takemi
authors.initials: T
authors.lastname: Enomoto
authors.forename: Kazuo
authors.initials: K
authors.lastname: Yamamoto
mesh_terms: D002453:Cell Cycle / Q000528:radiation effects; D004247:DNA / Q000378:metabolism / Q000528:radiation effects; D004260:DNA Repair; D019656:Loss of Heterozygosity; D008957:Models, Genetic; D016196:S Phase / Q000235:genetics / Q000528:radiation effects; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000528:radiation effects; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D004247:DNA