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First published online 5 February 2008
doi: 10.1242/jcs.021352

Journal of Cell Science 121, 590-600 (2008)
Published by The Company of Biologists 2008
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Research Article

Ku is involved in cell growth, DNA replication and G1-S transition

Emmanouil Rampakakis, Domenic Di Paola and Maria Zannis-Hadjopoulos*

McGill Cancer Centre and Department of Biochemistry, McGill University, Montreal, Quebec H3G 1Y6, Canada

* Author for correspondence (e-mail: maria.zannis{at}mcgill.ca)

Accepted 29 November 2007

The Ku protein (Ku70-Ku80) is involved in various genome-maintenance processes such as DNA replication and repair, telomere maintenance, and chromosomal stability. We previously found that Ku80 is implicated in the loading of members of the pre-replicative complex (pre-RC) onto replication origins. Here, we report that acute reduction of Ku80 to 10% of its normal levels leads to impaired DNA replication and activation of a replication stress checkpoint. In the absence of Ku80, decreased levels of the initiator proteins Orc1 and Orc6 as well as reduced chromatin binding of Orc1, Orc4 and Cdc45 were observed, leading to decreased origin firing, whereas Orc2 and Orc3 were unaffected. Prolonged perturbation of DNA replication caused the block of cell-cycle progression in late G1 phase with low Cdk2 activity due to increased p21 expression and decreased Cdc25A and Cdk2 levels. The data suggest the interplay between the DNA-replication and cell-cycle machineries and shed light on a new role of Ku in G1-S transition.

Key words: DNA replication, Ku, Cell growth, Nascent DNA, Replication stress checkpoint






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