Maltseva E A, Krasikova Y S, Naegeli H, Lavrik O I, Rechkunova N I
Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, 630090, Russia.
Biochemistry (Mosc). 2014 Jun;79(6):545-54. doi: 10.1134/S000629791406008X.
Xeroderma pigmentosum factor A (XPA) is one of the key proteins in the nucleotide excision repair (NER) process. The effects of point substitutions in the DNA-binding domain of XPA (positively charged lysine residues replaced by negatively charged glutamate residues: XPA K204E, K179E, K141E, and tandem mutant K141E/K179E) on the interaction of the protein with DNA structures modeling intermediates of the damage recognition and pre-incision stages in NER were analyzed. All these mutations decreased the affinity of the protein to DNA, the effect depending on the substitution and the DNA structure. The mutant as well as wild-type proteins bind with highest efficiency partly open damaged DNA duplex, and the affinity of the mutants to this DNA is reduced in the order: K204E > K179E >> K141E = K141/179E. For all the mutants, decrease in DNA binding efficiency was more pronounced in the case of full duplex and single-stranded DNA than with bubble-DNA structure, the difference between protein affinities to different DNA structures increasing as DNA binding activity of the mutant decreased. No effect of the studied XPA mutations on the location of the protein on the partially open DNA duplex was observed using photoinduced crosslinking with 5-I-dUMP in different positions of the damaged DNA strand. These results combined with earlier published data suggest no direct correlation between DNA binding and activity in NER for these XPA mutants.
着色性干皮病因子A(XPA)是核苷酸切除修复(NER)过程中的关键蛋白之一。分析了XPA DNA结合结构域中的点突变(带正电荷的赖氨酸残基被带负电荷的谷氨酸残基取代:XPA K204E、K179E、K141E以及串联突变体K141E/K179E)对该蛋白与模拟NER损伤识别和切口前期中间体的DNA结构相互作用的影响。所有这些突变均降低了蛋白与DNA的亲和力,其影响取决于取代情况和DNA结构。突变型和野生型蛋白均以最高效率结合部分开放的受损DNA双链体,突变体对该DNA的亲和力按以下顺序降低:K204E > K179E >> K141E = K141/179E。对于所有突变体,与泡状DNA结构相比,双链体DNA和单链DNA情况下的DNA结合效率降低更为明显,随着突变体DNA结合活性降低,蛋白对不同DNA结构的亲和力差异增大。在受损DNA链的不同位置使用5-I-dUMP进行光诱导交联,未观察到所研究的XPA突变对蛋白在部分开放DNA双链体上位置的影响。这些结果与早期发表的数据相结合表明,这些XPA突变体在NER中的DNA结合与活性之间没有直接相关性。