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Molecular and Cellular Biology, April 2000, p. 2358-2366, Vol. 20, No. 7
Gene Targeting Group, MRC Clinical Sciences
Centre, Imperial College School of Medicine, Hammersmith Hospital,
London W12 0NN, United Kingdom
Received 11 August 1999/Returned for modification 28 September
1999/Accepted 29 December 1999
Entry into mitosis is controlled by the cyclin-dependent kinase
CDK1 and can be delayed in response to DNA damage. In some systems,
such G2/M arrest has been shown to reflect the
stabilization of inhibitory phosphorylation sites on CDK1. In human
cells, full G2 arrest appears to involve additional
mechanisms. We describe here the prolonged (>6 day) downregulation of
CDK1 protein and mRNA levels following DNA damage in human cells. This
silencing of gene expression is observed in primary human fibroblasts
and in two cell lines with functional p53 but not in HeLa cells, where p53 is inactive. Silencing is accompanied by the accumulation of cells
in G2, when CDK1 expression is normally maximal. The response is impaired by mutations in cis-acting elements
(CDE and CHR) in the CDK1 promoter, indicating that silencing occurs at
the transcriptional level. These elements have previously been implicated in the repression of transcription during G1
that is normally lifted as cells progress into S and G2.
Interestingly, we find that other genes, including those for CDC25C,
cyclin A2, cyclin B1, CENP-A, and topoisomerase II
0270-7306/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Repression of CDK1 and Other Genes with CDE and CHR
Promoter Elements during DNA Damage-Induced G2/M Arrest
in Human Cells

, that are
normally expressed preferentially in G2 and whose promoter
regions include putative CDE and CHR elements are also downregulated in
response to DNA damage. These data, together with those of other
groups, support the existence of a p53-dependent, DNA damage-activated
pathway leading to CHR- and CDE-mediated transcriptional repression of various G2-specific genes. This pathway may be required
for sustained periods of G2 arrest following DNA damage.
*
Corresponding author. Mailing address: Gene Targeting
Group, MRC Clinical Sciences Centre, Imperial College School of
Medicine, Hammersmith Hospital, London W12 0NN, United Kingdom. Phone:
(44)-181-383-8276. Fax: (44)-181-383-8303. E-mail:
andy.porter{at}csc.mrc.ac.uk.
Present address: The Wellcome Trust, London NW1 2BE, United Kingdom.
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