UV induces GADD45 in a p53-dependent and -independent manner in human keratinocytes.

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.