title: The carboxy-terminal domain of the XPC protein plays a crucial role in nucleotide excision repair through interactions with transcription factor IIH.
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.
authors.affiliation: Institute for Molecular and Cellular Biology, Osaka University, 1-3 Yamada-oka, Suita, 565-0871, Osaka, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Uchida
authors.forename: Kaoru
authors.initials: K
authors.lastname: Sugasawa
authors.forename: Chikahide
authors.initials: C
authors.lastname: Masutani
authors.forename: Naoshi
authors.initials: N
authors.lastname: Dohmae
authors.forename: Marito
authors.initials: M
authors.lastname: Araki
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yokoi
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Ohkuma
authors.forename: Fumio
authors.initials: F
authors.lastname: Hanaoka
mesh_terms: D016367:Baculoviridae / Q000235:genetics; D002457:Cell Extracts; D002478:Cells, Cultured; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D017931:DNA Primers; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000502:physiology*; D005656:Fungal Proteins / Q000235:genetics*; D006639:Histidine / Q000737:chemistry; D006801:Humans; D008214:Lymphocytes; D016297:Mutagenesis, Site-Directed; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D017384:Sequence Deletion; D051758:Transcription Factor TFIIH; D019473:Transcription Factors, TFII / Q000378:metabolism*
chemical_list: D002457:Cell Extracts; D017931:DNA Primers; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D011994:Recombinant Proteins; D019473:Transcription Factors, TFII; D051758:Transcription Factor TFIIH; C086984:XPC protein, human; D006639:Histidine; D004247:DNA