title: CSB interacts with SNM1A and promotes DNA interstrand crosslink processing.
abstract: Cockayne syndrome (CS) is a premature aging disorder characterized by photosensitivity, impaired development and multisystem progressive degeneration, and consists of two strict complementation groups, A and B. Using a yeast two-hybrid approach, we identified the 5'-3' exonuclease SNM1A as one of four strong interacting partners of CSB. This direct interaction was confirmed using purified recombinant proteins-with CSB able to modulate the exonuclease activity of SNM1A on oligonucleotide substrates in vitro-and the two proteins were shown to exist in a common complex in human cell extracts. CSB and SNM1A were also found, using fluorescently tagged proteins in combination with confocal microscopy and laser microirradiation, to be recruited to localized trioxsalen-induced ICL damage in human cells, with accumulation being suppressed by transcription inhibition. Moreover, SNM1A recruitment was significantly reduced in CSB-deficient cells, suggesting coordination between the two proteins in vivo. CSB-deficient neural cells exhibited increased sensitivity to DNA crosslinking agents, particularly, in a non-cycling, differentiated state, as well as delayed ICL processing as revealed by a modified Comet assay and γ-H2AX foci persistence. The results indicate that CSB coordinates the resolution of ICLs, possibly in a transcription-associated repair mechanism involving SNM1A, and that defects in the process could contribute to the post-mitotic degenerative pathologies associated with CS.
authors.affiliation: Laboratory of Molecular Gerontology, National Institute on Aging, Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA.
authors.forename: Teruaki
authors.initials: T
authors.lastname: Iyama
authors.affiliation: Department of Oncology, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, OX3 9DS, UK.
authors.forename: Sook Y
authors.initials: SY
authors.lastname: Lee
authors.affiliation: Caliber Biotherapeutics, Bryan, TX 77807, USA.
authors.forename: Brian R
authors.initials: BR
authors.lastname: Berquist
authors.affiliation: The Structural Genomics Consortium, University of Oxford, Oxford, OX3 7DQ, UK.
authors.forename: Opher
authors.initials: O
authors.lastname: Gileadi
authors.affiliation: Laboratory of Molecular Gerontology, National Institute on Aging, Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA.
authors.forename: Vilhelm A
authors.initials: VA
authors.lastname: Bohr
authors.affiliation: Laboratory of Molecular Gerontology, National Institute on Aging, Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA.
authors.forename: Michael M
authors.initials: MM
authors.lastname: Seidman
authors.affiliation: Department of Oncology, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, OX3 9DS, UK.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: McHugh
authors.affiliation: Laboratory of Molecular Gerontology, National Institute on Aging, Intramural Research Program, National Institutes of Health, Baltimore, MD 21224, USA wilsonda@mail.nih.gov.
authors.forename: David M
authors.initials: DM
authors.lastname: Wilson
mesh_terms: D018797:Cell Cycle Proteins; D002460:Cell Line; D003432:Cross-Linking Reagents; D004247:DNA / Q000378:metabolism; D004249:DNA Damage; D004265:DNA Helicases / Q000378:metabolism*; D004260:DNA Repair; D045643:DNA Repair Enzymes / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D005090:Exodeoxyribonucleases; D005092:Exonucleases / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D000075223:Poly-ADP-Ribose Binding Proteins
chemical_list: D018797:Cell Cycle Proteins; D003432:Cross-Linking Reagents; D004268:DNA-Binding Proteins; D000075223:Poly-ADP-Ribose Binding Proteins; D004247:DNA; C115339:DCLRE1A protein, human; D005090:Exodeoxyribonucleases; D005092:Exonucleases; D004265:DNA Helicases; C078673:ERCC6 protein, human; D045643:DNA Repair Enzymes