Simpson Laura J, Ross Anna-Laura, Szüts Dávid, Alviani Cherry A, Oestergaard Vibe H, Patel Ketan J, Sale Julian E
Medical Research Council Laboratory of Molecular Biology, Division of Protein & Nucleic Acid Chemistry, Hills Road, Cambridge CB2 2QH, UK.
EMBO Rep. 2006 Sep;7(9):927-32. doi: 10.1038/sj.embor.7400777. Epub 2006 Aug 4.
Ubiquitination of proliferating-cell nuclear antigen (PCNA) at K164 by RAD6/RAD18 has a key role in DNA damage tolerance in yeast. Here, we report on the first genetic study of this modification in a vertebrate cell. As in yeast, mutation of K164 of PCNA to arginine in the avian cell line DT40 results in sensitivity to DNA damage but, by contrast, the DT40 pcnaK164R mutant is more sensitive than the rad18 mutant. Consistent with this, we show the presence of residual ubiquitination of PCNA at K164 in the absence of functional RAD18, suggesting the presence of an alternate PCNA ubiquitinating enzyme in DT40. Furthermore, RAD18 and PCNA K164 have non-overlapping roles in the suppression of sister chromatid exchange in DT40, showing that RAD18 has other functions that do not involve the ubiquitination of PCNA.
RAD6/RAD18在K164位点对增殖细胞核抗原（PCNA）进行泛素化修饰在酵母的DNA损伤耐受中起关键作用。在此，我们报道了对脊椎动物细胞中这种修饰的首次遗传学研究。与酵母一样，在禽类细胞系DT40中将PCNA的K164突变为精氨酸会导致对DNA损伤敏感，但相比之下，DT40 pcnaK164R突变体比rad18突变体更敏感。与此一致的是，我们发现在缺乏功能性RAD18的情况下，PCNA在K164位点存在残留泛素化，这表明DT40中存在一种替代的PCNA泛素化酶。此外，RAD18和PCNA K164在DT40中对姐妹染色单体交换的抑制作用中具有不重叠的作用，这表明RAD18具有其他不涉及PCNA泛素化的功能。
