title: UV induces GADD45 in a p53-dependent and -independent manner in human keratinocytes.
abstract: BACKGROUND
  GADD45 is a multifunctional protein involved in DNA repair and in cell cycle checkpoint control. p53 plays an important role in regulating DNA repair and in response to UVB in keratinocytes.
  
  
  OBJECTIVE
  GADD45 and p53 expression was examined and compared at the mRNA and protein level after exposure to UV irradiation.
  
  
  METHODS
  Human keratinocytes were exposed to increasing doses of UVB, and an RNA protection assay and a Western blot analysis were performed.
  
  
  RESULTS
  The RNase protection assays using human keratinocytes showed that GADD45 mRNA increases after 4 h and remains elevated for 24 h in cells irradiated at 100, 300, or 600 J/m2 UVB. The level of GADD45 protein increases after 8 h and remains elevated for 48 h, with maximal induction at 300 J/m2. p53 mRNA did not rise in concert with GADD45 at any dose used, and p53 protein was not up-regulated at the lower dose of 100 J/m2.
  
  
  CONCLUSIONS
  GADD45 is regulated in both a p53-dependent and a p53-independent manner in keratinocytes after UV exposure.
authors.affiliation: Department of Laboratory Medicine and Pathology, Faculty of Medicine, University of Alberta, Edmonton, Canada.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Maeda
authors.forename: Adrian B
authors.initials: AB
authors.lastname: Sim
authors.forename: Duane A
authors.initials: DA
authors.lastname: Leedel
authors.forename: Prescillia P S
authors.initials: PP
authors.lastname: Chua
authors.forename: Eugene G
authors.initials: EG
authors.lastname: Chomey
authors.forename: Le
authors.initials: L
authors.lastname: Luong
authors.forename: Victor A
authors.initials: VA
authors.lastname: Tron
mesh_terms: D015153:Blotting, Western; D005786:Gene Expression Regulation / Q000528:radiation effects*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D015603:Keratinocytes / Q000378:metabolism* / Q000528:radiation effects*; D011506:Proteins / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D014466:Ultraviolet Rays; D015854:Up-Regulation / Q000502:physiology; D000097642:GADD45 Proteins
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D011506:Proteins; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D000097642:GADD45 Proteins