title: Human HMGB1 directly facilitates interactions between nucleotide excision repair proteins on triplex-directed psoralen interstrand crosslinks.
abstract: Psoralen is a chemotherapeutic agent that acts by producing DNA interstrand crosslinks (ICLs), which are especially cytotoxic and mutagenic because their complex chemical nature makes them difficult to repair. Proteins from multiple repair pathways, including nucleotide excision repair (NER), are involved in their removal in mammalian cells, but the exact nature of their repair is poorly understood. We have shown previously that HMGB1, a protein involved in chromatin structure, transcriptional regulation, and inflammation, can bind cooperatively to triplex-directed psoralen ICLs with RPA, and that mammalian cells lacking HMGB1 are hypersensitive to psoralen ICLs. However, whether this effect is mediated by a role for HMGB1 in DNA damage recognition is still unknown. Given HMGB1's ability to bind to damaged DNA and its interaction with the RPA protein, we hypothesized that HMGB1 works together with the NER damage recognition proteins to aid in the removal of ICLs. We show here that HMGB1 is capable of binding to triplex-directed psoralen ICLs with the dedicated NER damage recognition complex XPC-RAD23B, as well as XPA-RPA, and that they form a higher-order complex on these lesions. In addition, we demonstrate that HMGB1 interacts with XPC-RAD23B and XPA in the absence of DNA. These findings directly demonstrate interactions between HMGB1 and the NER damage recognition proteins, and suggest that HMGB1 may affect ICL repair by enhancing the interactions between NER damage recognition factors.
authors.affiliation: Department of Carcinogenesis, The University of Texas MD Anderson Cancer Center, Science Park-Research Division, Smithville, TX 78957, USA.
authors.forename: Sabine S
authors.initials: SS
authors.lastname: Lange
authors.forename: Madhava C
authors.initials: MC
authors.lastname: Reddy
authors.forename: Karen M
authors.initials: KM
authors.lastname: Vasquez
mesh_terms: D000818:Animals; D026501:Blotting, Southwestern; D002460:Cell Line; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004249:DNA Damage; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D005363:Ficusin / Q000737:chemistry*; D024243:HMGB1 Protein / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D011485:Protein Binding; D011994:Recombinant Proteins / Q000378:metabolism; D051716:Replication Protein A / Q000378:metabolism; D018411:Spodoptera; D051760:Xeroderma Pigmentosum Group A Protein / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D024243:HMGB1 Protein; C513287:RAD23B protein, human; D011994:Recombinant Proteins; D051716:Replication Protein A; C497314:XPA protein, human; D051760:Xeroderma Pigmentosum Group A Protein; C051802:triplex DNA; C086984:XPC protein, human; D004247:DNA; D045643:DNA Repair Enzymes; D005363:Ficusin