Okuda Masahiko, Nakazawa Yuka, Guo Chaowan, Ogi Tomoo, Nishimura Yoshifumi
Graduate School of Medical Life Science, Yokohama City University, 1-7-29 Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan.
Department of Genome Repair, Atomic Bomb Disease Institute, Nagasaki University, 1-12-4, Sakamoto, Nagasaki 852-8523, Japan.
Nucleic Acids Res. 2017 Dec 15;45(22):13043-13055. doi: 10.1093/nar/gkx970.
Nucleotide excision repair is initiated by two different damage recognition subpathways, global genome repair (GGR) and transcription-coupled repair (TCR). In GGR, XPC detects DNA lesions and recruits TFIIH via interaction with the pleckstrin homology (PH) domain of TFIIH subunit p62. In TCR, an elongating form of RNA Polymerase II detects a lesion on the transcribed strand and recruits TFIIH by an unknown mechanism. Here, we found that the TCR initiation factor UVSSA forms a stable complex with the PH domain of p62 via a short acidic string in the central region of UVSSA, and determined the complex structure by NMR. The acidic string of UVSSA binds strongly to the basic groove of the PH domain by inserting Phe408 and Val411 into two pockets, highly resembling the interaction mechanism of XPC with p62. Mutational binding analysis validated the structure and identified residues crucial for binding. TCR activity was markedly diminished in UVSSA-deficient cells expressing UVSSA mutated at Phe408 or Val411. Thus, a common TFIIH recruitment mechanism is shared by UVSSA in TCR and XPC in GGR.
核苷酸切除修复由两种不同的损伤识别子途径启动，即全基因组修复（GGR）和转录偶联修复（TCR）。在GGR中，XPC检测DNA损伤，并通过与TFIIH亚基p62的pleckstrin同源（PH）结构域相互作用招募TFIIH。在TCR中，一种延伸形式的RNA聚合酶II检测转录链上的损伤，并通过未知机制招募TFIIH。在此，我们发现TCR起始因子UVSSA通过UVSSA中心区域的一段短酸性序列与p62的PH结构域形成稳定复合物，并通过核磁共振确定了复合物结构。UVSSA的酸性序列通过将Phe408和Val411插入两个口袋而与PH结构域的碱性凹槽强烈结合，这与XPC与p62的相互作用机制高度相似。突变结合分析验证了该结构，并确定了结合关键残基。在表达Phe408或Val411突变的UVSSA的UVSSA缺陷细胞中，TCR活性显著降低。因此，TCR中的UVSSA和GGR中的XPC共享一种共同的TFIIH招募机制。
