Cdc7 activates replication checkpoint by phosphorylating the Chk1 binding domain of Claspin in human cells

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Abstract

Replication checkpoint is essential for maintaining genome integrity in response to various replication stresses as well as during the normal growth. The evolutionally conserved ATR-Claspin-Chk1 pathway is induced during replication checkpoint activation. Cdc7 kinase, required for initiation of DNA replication at replication origins, has been implicated in checkpoint activation but how it is involved in this pathway has not been known. Here, we show that Cdc7 is required for Claspin-Chk1 interaction in human cancer cells by phosphorylating CKBD (Chk1-binding-domain) of Claspin. The residual Chk1 activation in Cdc7-depleted cells is lost upon further depletion of casein kinase1 (CK1g1), previously reported to phosphorylate CKBD. Thus, Cdc7, in conjunction with CK1g1, facilitates the interaction between Claspin and Chk1 through phosphorylating CKBD. We also show that, whereas Cdc7 is predominantly responsible for CKBD phosphorylation in cancer cells, CK1g1plays a major role in non-cancer cells, providing rationale for targeting Cdc7 for cancer cell-specific cell killing.

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All data generated or analyzed during this study are included in the manuscript and supporting files.Figure 1-source data 1 has been provided for Figure 1AFigure 4 -source data 1-3 have been provided for Figure 4Figure 5-figure supplement 2-source data 1 has been provided for Figure 5-figure supplement 2Figure 5-figure supplement 3-source data 1 has been provided for Figure 5-figure supplement 3BFigure 6-source data 1has been provided for Figure 6BFigure 7-source data 1 has been provided for Figure 7BFigure 7-source data 2 has been provided for Figure 7D

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Chi-Chun Yang

Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan

Competing interests
The authors declare that no competing interests exist.
Hiroyuki Kato

Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan

Competing interests
The authors declare that no competing interests exist.
Mayumi Shindo

Protein Analyses Laboratory, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan

Competing interests
The authors declare that no competing interests exist.
Hisao Masai

Department of Genome Medicine, Tokyo Metropolitan Institute of Medical Science, Tokyo, Japan

For correspondence
masai-hs@igakuken.or.jp

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0003-1268-5302

Funding

Japan Society for the Promotion of Science (23247031)

Hisao Masai

Japan Society for the Promotion of Science (26251004)

Hisao Masai

Japan Society for the Promotion of Science (24114520)

Hisao Masai

Japan Society for the Promotion of Science (25125724)

Hisao Masai

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

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This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.