The C-terminal domain of the XPC protein plays a crucial role in nucleotide excision repair through interactions with transcription factor IIH

Institute for Molecular and Cellular Biology, Osaka University, 1-3 Yamada-oka, Suita, 565-0871, Osaka, Japan.
DNA Repair (Impact Factor: 3.36). 07/2002; 1(6):449-61. DOI: 10.1016/S1568-7864(02)00031-9
Source: PubMed

ABSTRACT The xeroderma pigmentosum group C (XPC) protein specifically involved in genome-wide damage recognition for nucleotide excision repair (NER) was purified as a tight complex with HR23B, one of the two mammalian homologs of RAD23 in budding yeast. This XPC-HR23B complex exhibits strong binding affinity for single-stranded DNA, as well as preferential binding to various types of damaged DNA. To examine the structure-function relationship of XPC, a series of truncated mutant proteins were generated and assayed for various binding activities. The two domains participating in binding to HR23B and damaged DNA, respectively, were mapped within the carboxy-terminal half of XPC, which also contains an evolutionary conserved amino acid sequence homologous to the yeast RAD4 protein. We established that the carboxy-terminal 125 amino acids are dispensable for both HR23B and damaged DNA binding, while interactions with transcription factor IIH (TFIIH) are significantly impaired by truncation of this domain. Furthermore, deletion of the extreme carboxy-terminal domain totally abolished XPC activity in the cell-free NER reaction. These results suggest that following initial damage recognition, the carboxy terminus of XPC may be essential for the recruitment of TFIIH, and that most truncation mutations identified in XP-C patients result in non-functional proteins.

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    • "Particularly, the XPC–hHR23B and XPA–RPA protein complexes are involved in the initial detection of damaged DNA in mammalian NER (Kobayashi et al., 1998), suggesting that XPC transcript would be induced as early signals of DNA damage in the gamma-irradiated K. marmoratus larvae. Subsequently, TFIIH complex (XPG, XPB, XPD, GTF2H1/p62, GTF2H2/p44, GTF2H3/p34 and GTF2H4/p52) participates to recognize the lesion by directly interacting with the XPC complex (Uchida et al., 2002). Wang et al. (2004) reported that XPCdefective cells negatively affect the expression of some DSB repair genes, cell cycle-related genes, apoptosis-related genes in the cisplatin treatment, which is known to be a DNA damage inducer. "
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    • "The DNA-binding domain of XPC is localized between amino acid 607 and 742. Interestingly, the RAD23A-or RAD23B- binding region is between amino acid 496 and 734 (Uchida et al., 2002) and thus partially overlaps with the DNA-binding area. Therefore, it is tempting to speculate that the dissociation of RAD23B upon UV irradiation is necessary to make the "
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    • "The Nterminal region of human XPC is responsible for an association with XPA [41]. On the other hand, the carboxy-terminal tail of XPC protein harbors domains that interact with centrin-2 (residues 847–863) and TFIIH (residues 816–940) [30] [44] "
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    ABSTRACT: The recognition and subsequent repair of DNA damage are essential reactions for the maintenance of genome stability. A key general sensor of DNA lesions is xeroderma pigmentosum group C (XPC) protein, which recognizes a wide variety of helix-distorting DNA adducts arising from ultraviolet (UV) radiation, genotoxic chemicals and reactive metabolic byproducts. By detecting damaged DNA sites, this unique molecular sensor initiates the global genome repair (GGR) pathway, which allows for the removal of all the aforementioned lesions by a limited repertoire of excision factors. A faulty GGR activity causes the accumulation of DNA adducts leading to mutagenesis, carcinogenesis, neurological degeneration and other traits of premature aging. Recent findings indicate that XPC protein achieves its extraordinary substrate versatility by an entirely indirect readout strategy implemented in two clearly discernible stages. First, the XPC subunit uses a dynamic sensor interface to monitor the double helix for the presence of non-hydrogen-bonded bases. This initial screening generates a transient nucleoprotein intermediate that subsequently matures into the ultimate recognition complex by trapping undamaged nucleotides in the abnormally oscillating native strand, in a way that no direct contacts are made between XPC protein and the offending lesion itself. It remains to be elucidated how accessory factors like Rad23B, centrin-2 or the UV-damaged DNA-binding complex contribute to this dynamic two-stage quality control process.
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