title: GADD45 regulates G2/M arrest, DNA repair, and cell death in keratinocytes following ultraviolet exposure.
abstract: GADD45 is a multifunctional protein that is regulated by p53. p53 plays an important role in regulating DNA repair and in the response to ultraviolet light in keratinocytes. This study investigates the role of GADD45 in the response to ultraviolet B. Cell cycle analysis demonstrated that wild-type and Gadd45-deficient cells have transient G2/M arrest, but only in the wild-type cells was arrest sustained. Cdc2 kinase activity in immunoprecipitates from normal and Gadd45-deficient cells decreases after irradiation in normal cells but not in Gadd45-deficient cells. An immunofluorescent study with Cdc2 antibody demonstrated diffuse cellular fluorescence before ultraviolet irradiation in both Gadd45-deficient and wild-type cells, but upon ultraviolet irradiation only Gadd45-proficient cells showed Cdc2 sequestration in the cytoplasm. Gadd45-deficient cells also have a slower rate of nucleotide excision repair. The lack of G2/M arrest coupled with reduced DNA repair leads to a higher ultraviolet sensitivity of Gadd45-deficient cells. These results reveal that GADD45 promotes G2/M arrest via nuclear export and kinase activity of Cdc2, increases global genomic DNA repair, and inhibits cell death in keratinocytes. Thus, GADD45 plays an important role in maintaining genomic integrity in ultraviolet-exposed skin.
authors.affiliation: Department of Laboratory Medicine and Pathology, University of Alberta, Faculty of Medicine, 4B1 W.C. Mackenzie Health Science Center, 8440-112th Street, Edmonton, Alberta, Canada T6G 2B7.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Maeda
authors.forename: Atef N
authors.initials: AN
authors.lastname: Hanna
authors.forename: Adrian B
authors.initials: AB
authors.lastname: Sim
authors.forename: Prescillia P
authors.initials: PP
authors.lastname: Chua
authors.forename: Michelle T
authors.initials: MT
authors.lastname: Chong
authors.forename: Victor A
authors.initials: VA
authors.lastname: Tron
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D016203:CDC2 Protein Kinase / Q000378:metabolism; D018797:Cell Cycle Proteins; D016923:Cell Death / Q000502:physiology* / Q000528:radiation effects; D004260:DNA Repair / Q000502:physiology*; D016195:G2 Phase / Q000502:physiology / Q000528:radiation effects; D015870:Gene Expression / Q000528:radiation effects; D015603:Keratinocytes / Q000166:cytology* / Q000201:enzymology / Q000528:radiation effects; D051379:Mice; D008822:Mice, Transgenic; D008938:Mitosis / Q000502:physiology / Q000528:radiation effects; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D014466:Ultraviolet Rays / Q000009:adverse effects; D000097642:GADD45 Proteins
chemical_list: D016203:CDC2 Protein Kinase; D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; C499072:Gadd45a protein, mouse; D000097642:GADD45 Proteins