Fishman-Lobell J, Haber J E
Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, MA 02254.
Science. 1992 Oct 16;258(5081):480-4. doi: 10.1126/science.1411547.
Double-strand breaks (DSBs) in Saccharomyces cerevisiae can be repaired by gene conversions or by deletions resulting from single-strand annealing between direct repeats of homologous sequences. Although rad1 mutants are resistant to x-rays and can complete DSB-mediated mating-type switching, they could not complete recombination when the ends of the break contained approximately 60 base pairs of nonhomology. Recombination was restored when the ends of the break were made homologous to donor sequences. Additionally, the absence of RAD1 led to the frequent appearance of a previously unobserved type of recombination product. These data suggest RAD1 is required to remove nonhomologous DNA from the 3' ends of recombining DNA, a process analogous to the excision of photodimers during repair of ultraviolet-damaged DNA.
酿酒酵母中的双链断裂（DSB）可通过基因转换或同源序列直接重复之间单链退火导致的缺失来修复。虽然rad1突变体对X射线有抗性，并且可以完成DSB介导的交配型转换，但当断裂末端包含约60个碱基对的非同源性时，它们无法完成重组。当断裂末端与供体序列同源时，重组得以恢复。此外，RAD1的缺失导致一种以前未观察到的重组产物频繁出现。这些数据表明，RAD1是从重组DNA的3'末端去除非同源DNA所必需的，这一过程类似于紫外线损伤DNA修复过程中光二聚体的切除。
