Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
Biochemistry and Molecular Biophysics Graduate Group, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
Nat Commun. 2021 Jun 7;12(1):3338. doi: 10.1038/s41467-021-23684-x.
The versatile nucleotide excision repair (NER) pathway initiates as the XPC-RAD23B-CETN2 complex first recognizes DNA lesions from the genomic DNA and recruits the general transcription factor complex, TFIIH, for subsequent lesion verification. Here, we present a cryo-EM structure of an NER initiation complex containing Rad4-Rad23-Rad33 (yeast homologue of XPC-RAD23B-CETN2) and 7-subunit coreTFIIH assembled on a carcinogen-DNA adduct lesion at 3.9-9.2 Å resolution. A ~30-bp DNA duplex could be mapped as it straddles between Rad4 and the Ssl2 (XPB) subunit of TFIIH on the 3' and 5' side of the lesion, respectively. The simultaneous binding with Rad4 and TFIIH was permitted by an unwinding of DNA at the lesion. Translocation coupled with torque generation by Ssl2 and Rad4 would extend the DNA unwinding at the lesion and deliver the damaged strand to Rad3 (XPD) in an open form suitable for subsequent lesion scanning and verification.
多功能核苷酸切除修复 (NER) 途径的起始是 XPC-RAD23B-CETN2 复合物首先识别来自基因组 DNA 的 DNA 损伤，并募集一般转录因子复合物 TFIIH，以进行后续的损伤验证。在这里，我们呈现了一个包含 Rad4-Rad23-Rad33（酵母中 XPC-RAD23B-CETN2 的同源物）和 7 个亚基核心 TFIIH 的 NER 起始复合物的冷冻电镜结构，该复合物组装在致癌剂-DNA 加合物损伤上，分辨率为 3.9-9.2 Å。大约 30 个碱基对的 DNA 双链可以被映射，因为它分别跨越损伤处 Rad4 和 TFIIH 的 Ssl2（XPB）亚基的 3'和 5'侧。通过在损伤处解旋 DNA，Rad4 和 TFIIH 可以同时结合。由 Ssl2 和 Rad4 产生的转位伴随着扭矩的产生，将在损伤处延伸 DNA 解旋，并将受损链以开放形式递送到 Rad3（XPD），以便后续进行损伤扫描和验证。
