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Open Access Highly Accessed Research

A phospho-proteomic screen identifies substrates of the checkpoint kinase Chk1

Melanie Blasius1, Josep V Forment1, Neha Thakkar1, Sebastian A Wagner2, Chunaram Choudhary2 and Stephen P Jackson1*

Author Affiliations

1 The Gurdon Institute and Department of Biochemistry, University of Cambridge, Tennis Court Road, Cambridge CB2 1QN, UK

2 NNF Center for Protein Research, Faculty of Health Sciences, University of Copenhagen, Blegdamsvej 3B, Copenhagen DK-2200, Denmark

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Genome Biology 2011, 12:R78  doi:10.1186/gb-2011-12-8-r78

Published: 18 August 2011

Abstract

Background

The cell-cycle checkpoint kinase Chk1 is essential in mammalian cells due to its roles in controlling processes such as DNA replication, mitosis and DNA-damage responses. Despite its paramount importance, how Chk1 controls these functions remains unclear, mainly because very few Chk1 substrates have hitherto been identified.

Results

Here, we combine a chemical genetics approach with high-resolution mass spectrometry to identify novel Chk1 substrates and their phosphorylation sites. The list of targets produced reveals the potential impact of Chk1 function not only on processes where Chk1 was already known to be involved, but also on other key cellular events such as transcription, RNA splicing and cell fate determination. In addition, we validate and explore the phosphorylation of transcriptional co-repressor KAP1 Ser473 as a novel DNA-damage-induced Chk1 site.

Conclusions

By providing a substantial set of potential Chk1 substrates, we present opportunities for studying unanticipated functions for Chk1 in controlling a wide range of cellular processes. We also refine the Chk1 consensus sequence, facilitating the future prediction of Chk1 target sites. In addition, our identification of KAP1 Ser473 phosphorylation as a robust readout for Chk1 activity could be used to explore the in vivo effects of Chk1 inhibitors that are being developed for clinical evaluation.