UV radiation is a transcriptional inducer of p21(Cip1/Waf1) cyclin- kinase inhibitor in a p53-independent manner

Tarja Haapajärvi, Laura Kivinen, Annamari Heiskanen, Charles Des Bordes, Michael B. Datto, Xiao Fan Wang, Marikki Laiho

Research output: Contribution to journalArticlepeer-review

56 Scopus citations


p53 target genes p21(Cip1/Waf1) cyclin-kinase inhibitor (p21 CKI), GADD45, bax, and cyclin G and genes affecting the redox state of the cells are implicated in p53 damage control responses. In order to attribute their functions and dependency of p53 in UV-damaged cells we undertook an analysis of UVC responses of fibroblasts derived from p53 knock-out mice. UVC radiation efficiently and rapidly inhibited DNA replication in both p53 -/- and +/+ cells. The arrest was persistent in p53 -/- fibroblasts and cells underwent apoptosis, whereas p53 +/+ cells recovered and reentered the cycle. Protein and mRNA analyses of p21 expression showed that it was induced up to sixfold with similar kinetics both in the presence and in the absence of p53. However, high doses of UV abrogated the p21 response in p53 -/- cells, whereas it was maintained in cells with normal p53. UVC radiation transcriptionally activated p21 expression as demonstrated by luciferase reporter assays using deletion constructs of the p21 promoter. The promoter assays further confirmed the independency of p53-binding sites in the activation and linked UV-responsive transcriptional regulation of p21 to two Sp1 consensus binding sites within -61 bp of the transcription initiation site. A weaker regulation was mediated by elements between -1300 to -500 bp relative to the transcription initiation site. The results suggest that in fibroblasts UVC radiation is a rapid and efficient inducer of p21 expression also in a p53-independent manner.

Original languageEnglish (US)
Pages (from-to)272-279
Number of pages8
JournalExperimental cell research
Issue number1
StatePublished - Apr 10 1999
Externally publishedYes


  • Cell cycle
  • Cyclin-kinase inhibitors
  • DNA damage
  • Posttranscriptional modification
  • Transcriptional regulation

ASJC Scopus subject areas

  • Cell Biology


Dive into the research topics of 'UV radiation is a transcriptional inducer of p21(Cip1/Waf1) cyclin- kinase inhibitor in a p53-independent manner'. Together they form a unique fingerprint.

Cite this