Magaña-Schwencke N, Henriques J A, Chanet R, Moustacchi E
Proc Natl Acad Sci U S A. 1982 Mar;79(6):1722-6. doi: 10.1073/pnas.79.6.1722.
In Saccharomyces cerevisiae, after 8-methoxypsoralen [8-(OMe)Ps] photoaddition, more crosslinks are induced per unit dose in mitochondrial DNA than in nuclear DNA. In wild-type cells treated in the exponential phase of growth, single- and double-strand breaks are produced during crosslink removal and then are rejoined upon postexposure incubation. The incision step is almost blocked in the rad 3-2 mutant, which is also defective in excision-repair of UV-induced (254 nm) pyrimidine dimers. The cutting of crosslinks from nuclear DNA is depressed in wild-type stationary-phase cells. This is correlated with a higher sensitivity of such cells to 8-(OMe)Ps photoinduced cell killing. The incision of crosslinks is dramatically reduced in mitochondrial DNA. The rejoining of single- and double-strand breaks is not only dependent on the product of the RAD51 gene (as shown by others) but also of the PSO2 gene. A correlation was found between the ability to recombine and strand rejoining. Therefore, as in bacteria, both the excision and the recombinational repair systems are involved in crosslink repair in yeast. However, double-strand breaks in yeast constitute repair intermediates which are not detected in Escherichia coli. The LD37 (dose necessary to induce a mean of one lethal hit per cell) corresponds to about 120 crosslinks per genome in exponential-phase cells of the wild type and to 1-2 crosslinks in the pso2-1 mutant.
在酿酒酵母中，8-甲氧基补骨脂素[8-(OMe)Ps]光加成后，线粒体DNA中每单位剂量诱导产生的交联比核DNA更多。在指数生长期处理的野生型细胞中，交联去除过程中会产生单链和双链断裂，然后在暴露后孵育时重新连接。在rad 3-2突变体中，切口步骤几乎被阻断，该突变体在紫外线诱导（254 nm）嘧啶二聚体的切除修复方面也存在缺陷。野生型静止期细胞中核DNA交联的切割受到抑制。这与此类细胞对8-(OMe)Ps光诱导细胞杀伤的更高敏感性相关。线粒体DNA中交联的切口显著减少。单链和双链断裂的重新连接不仅依赖于RAD51基因的产物（如其他人所示），还依赖于PSO2基因。发现重组能力与链重新连接之间存在相关性。因此，与细菌一样，切除和重组修复系统都参与了酵母中的交联修复。然而，酵母中的双链断裂构成了修复中间体，这在大肠杆菌中未被检测到。野生型指数期细胞的LD37（每细胞平均诱导一次致死性损伤所需的剂量）对应于每个基因组约120个交联，而在pso2-1突变体中为1-2个交联。
