title: Differential DNA lesion formation and repair in heterochromatin and euchromatin.
abstract: Discretely orchestrated chromatin condensation is important for chromosome protection from DNA damage. However, it is still unclear how different chromatin states affect the formation and repair of nucleotide excision repair (NER) substrates, e.g. ultraviolet (UV)-induced cyclobutane pyrimidine dimers (CPD) and the pyrimidine (6-4) pyrimidone photoproducts (6-4PP), as well as cisplatin-induced intrastrand crosslinks (Pt-GG). Here, by using immunofluorescence and chromatin immunoprecipitation assays, we have demonstrated that CPD, which cause minor distortion of DNA double helix, can be detected in both euchromatic and heterochromatic regions, while 6-4PP and Pt-GG, which cause major distortion of DNA helix, can exclusively be detected in euchromatin, indicating that the condensed chromatin environment specifically interferes with the formation of these DNA lesions. Mechanistic investigation revealed that the class III histone deacetylase SIRT1 is responsible for restricting the formation of 6-4PP and Pt-GG in cells, probably by facilitating the maintenance of highly condensed heterochromatin. In addition, we also showed that the repair of CPD in heterochromatin is slower than that in euchromatin, and DNA damage binding protein 2 (DDB2) can promote the removal of CPD from heterochromatic region. In summary, our data provide evidence for differential formation and repair of DNA lesions that are substrates of NER. Both the sensitivity of DNA to damage and the kinetics of repair can be affected by the underlying level of chromatin compaction.
authors.affiliation: Department of Radiology and.
authors.forename: Chunhua
authors.initials: C
authors.lastname: Han
authors.affiliation: James Cancer Hospital and Solove Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA.
authors.forename: Amit Kumar
authors.initials: AK
authors.lastname: Srivastava
authors.affiliation: Department of Radiology and.
authors.forename: Tiantian
authors.initials: T
authors.lastname: Cui
authors.affiliation: Department of Radiology and James Cancer Hospital and Solove Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA qi-en.wang@osumc.edu.
authors.forename: Qi-En
authors.initials: QE
authors.lastname: Wang
authors.affiliation: Department of Radiology and James Cancer Hospital and Solove Research Institute, The Ohio State University Wexner Medical Center, Columbus, OH 43210, USA qi-en.wang@osumc.edu.
authors.forename: Altaf A
authors.initials: AA
authors.lastname: Wani
mesh_terms: D002478:Cells, Cultured; D047369:Chromatin Immunoprecipitation; D004249:DNA Damage / Q000502:physiology*; D004260:DNA Repair / Q000502:physiology*; D022041:Euchromatin / Q000737:chemistry*; D005455:Fluorescent Antibody Technique; D006570:Heterochromatin / Q000737:chemistry*; D006801:Humans; D015151:Immunoblotting; D011740:Pyrimidine Dimers / Q000378:metabolism; D034622:RNA Interference
chemical_list: D022041:Euchromatin; D006570:Heterochromatin; D011740:Pyrimidine Dimers