Tripartite DNA Lesion Recognition and Verification by XPC, TFIIH, and XPA in Nucleotide Excision Repair

Transcription factor IIH (TFIIH) is essential for both transcription and nucleotide excision repair (NER). DNA lesions are initially detected by NER factors XPC and XPE or stalled RNA polymerases, but only bulky lesions are preferentially repaired by NER. To elucidate substrate specificity in NER, we have prepared homogeneous human ten-subunit TFIIH and its seven-subunit core (Core7) without the CAK module and show that bulky lesions in DNA inhibit the ATPase and helicase activities of both XPB and XPD in Core7 to promote NER, whereas non-genuine NER substrates have no such effect. Moreover, the NER factor XPA activates unwinding of normal DNA by Core7, but inhibits the Core7 helicase activity in the presence of bulky lesions. Finally, the CAK module inhibits DNA binding by TFIIH and thereby enhances XPC-dependent specific recruitment of TFIIH. Our results support a tripartite lesion verification mechanism involving XPC, TFIIH, and XPA for efficient NER. [Display omitted] •Human ten-subunit TFIIH and its seven-subunit Core7 were purified to homogeneity•Bulky lesions in DNA inhibit both the XPB and XPD helicase activities of Core7•XPA further inhibits the Core7 helicase activity in the presence of a bulky lesion•The CAK module enhances lesion-dependent recruitment of TFIIH by XPC in NER Nucleotide-excision repair (NER) is essential for mutation avoidance and genome maintenance. However, NER also contributes to drug resistance and reduced efficacy of chemotherapy. Elucidating the molecular mechanism of DNA lesion recognition in NER leads to better understanding of genetic disorders and improved diagnosis and treatment of a number of diseases.