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Role for Plk1 Phosphorylation of Hbo1 in Regulation of Replication Licensing

Zhao-Qiu Wu and Xiaoqi Liu
Proceedings of the National Academy of Sciences of the United States of America
Vol. 105, No. 6 (Feb. 12, 2008), pp. 1919-1924
Stable URL: http://www.jstor.org/stable/25451389
Page Count: 6
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Role for Plk1 Phosphorylation of Hbo1 in Regulation of Replication Licensing
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Abstract

In a search for Polo-like kinase 1 (Plk1)-interacting proteins using a yeast two-hybrid system, we have identified histone acetyltransferase binding to the origin recognition complex 1 (Hbo1) as a potential Plk1 target. Here, we show that the interaction between Plk1 and Hbo1 is mitosis-specific and that Plk1 phosphorylates Hbo1 on Ser-57 in vitro and in vivo. During mitosis, Cdk1 phosphorylates Hbo1 on Thr-85/88, creating a docking site for Plk1 to be recruited. Significantly, the overexpression of Hbo1 mutated at the Plk1 phosphorylation site (S57A) leads to cell-cycle arrest in the G₁/S phase, inhibition of chromatin loading of the minichromosome maintenance (Mcm) complex, and a reduced DNA replication rate. Similarly, Hbo1 depletion results in decreased DNA replication and a failure of Mcm complex binding to chromatin, both of which can be partially rescued by the ectopic expression of WT Hbo1 but not Hbo1-S57A. These results suggest that Plk1 phosphorylation of Hbo1 may be required for prereplicative complex (pre-RC) formation and DNA replication licensing.

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