Ultraviolet-B-induced G1 arrest is mediated by downregulation of cyclin-dependent kinase 4 in transformed keratinocytes lacking functional p53

J Invest Dermatol. 2002 May;118(5):818-24. doi: 10.1046/j.1523-1747.2002.01734.x.

Abstract

In order to identify potential novel targets for ultraviolet-B-induced skin tumorigenesis, we assessed the effect of ultraviolet-B exposure on cell cycle progression of transformed keratinocytes with mutant p53. We show that ultraviolet-B exposure of human epidermoid carcinoma A431 cells results in G1 cell cycle arrest in both asynchronously growing and synchronized cells. A significant increase in G1 cell population was observed following exposure to doses of ultraviolet-B as low as 10 mJ per cm2. When irradiated with ultraviolet-B, cells synchronized in G1 with mimosine did not exit G1. G1 cell cycle arrest was associated with a decrease in the hyperphosphorylated forms of retinoblastoma protein that was detectable within 4 h and gradually disappeared by 12 h. We also observed a decrease in cyclins D1, D2, and D3, and cyclin-dependent kinase 4 proteins, and a concomitant decrease in cyclin-dependent kinase 4/cyclin D1 associated kinase activity, whereas ultraviolet-B exposure had no effect on cyclin-dependent kinase 2 and cyclin-dependent kinase 6 levels during this time period. Incubation of cells with proteasome inhibitors MG-115 and MG-132 prevented the decrease in cyclin D1, D2, and D3, and cyclin-dependent kinase 4 protein. Taken together, our results suggest that ultraviolet-B-induced cell cycle arrest in A431 cells is mediated by cyclin-dependent kinase 4 downregulation. This identifies a novel pathway for G1 cell cycle arrest in transformed keratinocytes following ultraviolet-B irradiation.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Carcinoma, Squamous Cell
  • Cell Line, Transformed
  • Cyclin D1 / genetics
  • Cyclin D1 / metabolism
  • Cyclin-Dependent Kinase 4
  • Cyclin-Dependent Kinases / genetics
  • Cyclin-Dependent Kinases / metabolism*
  • Cysteine Endopeptidases
  • Down-Regulation / radiation effects
  • G1 Phase / radiation effects*
  • Gene Expression Regulation, Enzymologic / radiation effects
  • Humans
  • Keratinocytes / cytology
  • Keratinocytes / enzymology*
  • Keratinocytes / radiation effects
  • Multienzyme Complexes / antagonists & inhibitors
  • Phosphorylation
  • Proteasome Endopeptidase Complex
  • Proto-Oncogene Proteins*
  • RNA, Messenger / analysis
  • Retinoblastoma Protein / metabolism
  • Skin Neoplasms
  • Tumor Cells, Cultured
  • Tumor Suppressor Protein p53 / genetics*
  • Ultraviolet Rays

Substances

  • Multienzyme Complexes
  • Proto-Oncogene Proteins
  • RNA, Messenger
  • Retinoblastoma Protein
  • Tumor Suppressor Protein p53
  • Cyclin D1
  • CDK4 protein, human
  • Cyclin-Dependent Kinase 4
  • Cyclin-Dependent Kinases
  • Cysteine Endopeptidases
  • Proteasome Endopeptidase Complex