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UV induces GADD45 in a p53-dependent and -independent manner in human keratinocytes
Tomoko Maeda1, Adrian B Sim, Duane A Leedel
1Department of Laboratory Medicine and Pathology, Faculty of Medicine, University of Alberta, Edmonton, Canada.
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.
Conclusion:
GADD45 is regulated in both a p53-dependent and a p53-independent manner in keratinocytes after UV exposure.