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.
[Show abstract][Hide abstract] ABSTRACT: In nucleotide excision repair (NER), damage recognition by XPC-hHR23b is described as a critical step in the formation of the preincision complex (PInC) further composed of TFIIH, XPA, RPA, XPG, and ERCC1-XPF. To obtain new molecular insights into the assembly of the PInC, we analyzed its formation independently of DNA damage by using the lactose operator/repressor reporter system. We observed a sequential and ordered self-assembly of the PInC operating upon immobilization of individual NER factors on undamaged chromatin and mimicking that functioning on a bona fide NER substrate. We also revealed that the recruitment of the TFIIH subunit TTDA, involved in trichothiodystrophy group A disorder (TTD-A), was key in the completion of the PInC. TTDA recruits XPA through its first 15 amino acids, depleted in some TTD-A patients. More generally, these results show that proteins forming large nuclear complexes can be recruited sequentially on chromatin in the absence of their natural DNA target and with no reciprocity in their recruitment.
The Journal of Cell Biology 08/2014; 206(5). DOI:10.1083/jcb.201403096 · 9.83 Impact Factor
"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. "
[Show abstract][Hide abstract] ABSTRACT: To investigate effects of gamma ray irradiation in the hermaphroditic fish, Kryptolebias marmoratus larvae, we checked expression of p53, DNA repair, and heat shock protein genes with several antioxidant enzyme activities by quantitative real-time RT-PCR and biochemical methods in response to different doses of gamma radiation. As a result, the level of gamma radiation-induced DNA damage was initiated after 4Gy of radiation, and biochemical and molecular damage became substantial from 8Gy. In particular, several DNA repair mechanism-related genes were significantly modulated in the 6Gy gamma radiation-exposed fish larvae, suggesting that upregulation of such DNA repair genes was closely associated with cell survival after gamma irradiation. The mRNA expression of p53 and most hsps was also significantly upregulated at high doses of gamma radiation related to cellular damage. This finding indicates that gamma radiation can induce oxidative stress with associated antioxidant enzyme activities, and linked to modulation of the expression of DNA repair-related genes as one of the defense mechanisms against radiation damage. This study provides a better understanding of the molecular mode of action of defense mechanisms upon gamma radiation in fish larvae.
"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 "
[Show abstract][Hide abstract] ABSTRACT: The recognition of helix-distorting deoxyribonucleic acid (DNA) lesions by the
global genome nucleotide excision repair subpathway is performed by the
XPC–RAD23–CEN2 complex. Although it has been established that
Rad23 homologs are essential to protect XPC from proteasomal degradation, it is
unclear whether RAD23 proteins have a direct role in the recognition of DNA
damage. In this paper, we show that the association of XPC with
ultraviolet-induced lesions was impaired in the absence of RAD23 proteins.
Furthermore, we show that RAD23 proteins rapidly dissociated from XPC upon
binding to damaged DNA. Our data suggest that RAD23 proteins facilitate lesion
recognition by XPC but do not participate in the downstream DNA repair
The Journal of Cell Biology 03/2012; 196(6):681-8. DOI:10.1083/jcb.201107050 · 9.83 Impact Factor
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