Abstract
The xeroderma pigmentosum group C protein complex XPC-HR23B was first isolated as a factor that complemented nucleotide excision repair defects of XP-C cell extracts in vitro. Recent studies have revealed that this protein complex plays an important role in the early steps of global genome nucleotide excision repair, especially in damage recognition, open complex formation, and repair protein complex formation. However, the precise function of XPC-HR23B in global genome repair is still unclear. Here we demonstrate that XPC-HR23B interacts with general transcription factor IIH (TFIIH) both in vivo and in vitro. This interaction is thought to be mediated through the specific affinity of XPC for the TFIIH subunits XPB and/or p62, which are essential for both basal transcription and nucleotide excision repair. Interestingly, association of TFIIH with DNA was observed in both wild-type and XP-A cell extracts but not in XP-C cell extracts, and XPC-HR23B could restore the association of TFIIH with DNA in XP-C cell extracts. Moreover, we found that XPC-HR23B was necessary for efficient association of TFIIH with damaged DNA in cell-free extracts. We conclude that the XPC-HR23B protein complex plays a crucial role in the recruitment of TFIIH to damaged DNA in global genome repair.
Highlights
The xeroderma pigmentosum group C protein complex XPC-HR23B was first isolated as a factor that complemented nucleotide excision repair defects of XP-C cell extracts in vitro
Direct Interaction between XPC and transcription factor IIH (TFIIH)—Of the mammalian Nucleotide excision repair (NER) factors identified to date, only TFIIH has been suggested to interact with XPC [31,32,33], conclusive evidence of such interaction has been lacking
TFIIH purified from HeLa nuclear extracts (Fig. 2C) was incubated with glutathione-Sepharose beads bound to GST-rHR23B fusion protein that had been preincubated with or without Recombinant XPC (rXPC)
Summary
The xeroderma pigmentosum group C protein complex XPC-HR23B was first isolated as a factor that complemented nucleotide excision repair defects of XP-C cell extracts in vitro. We conclude that the XPC-HR23B protein complex plays a crucial role in the recruitment of TFIIH to damaged DNA in global genome repair. The xeroderma pigmentosum group C protein complex XPCHR23B is a tightly associated complex of the products of the XPC and HR23B genes and was initially purified from HeLa cell nuclear extracts as a protein factor that complemented the DNA repair defects of XP-C whole cell extracts in a cell-free NER reaction [14, 15]. We conclude that XPC-HR23B is necessary for recruitment of TFIIH to damaged DNA
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