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Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
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Inhibition of Cdc7/Dbf4 kinase activity affects specific phosphorylation sites on MCM2 in cancer cells

Deborah H Charych1, Mazie Coyne, Asha Yabannavar

  • 1Novartis Institute of Biomedical Research, Oncology, Emeryville, California 94608, USA. deb.charych@fiveprime.com

Journal of Cellular Biochemistry
|February 21, 2008
PubMed

Insights

Researchers identified new phosphorylation sites on MCM2, crucial for DNA replication initiation. This discovery provides novel read-outs for targeting Cdc7/Dbf4 kinase in cancer therapy.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Biochemistry

Background:

  • The Cdc7/Dbf4 kinase complex is essential for initiating DNA replication and maintaining genomic stability during replication stress.
  • Its precise mechanisms of action, particularly its interaction with the minichromosome maintenance (MCM) complex, require further elucidation.
  • Cdc7/Dbf4 is known to phosphorylate MCM proteins, influencing DNA replication progression.

Purpose of the Study:

  • To identify novel phosphorylation sites on the MCM2 protein mediated by the Cdc7/Dbf4 kinase.
  • To develop specific antibodies against these novel phosphorylation sites as potential biomarkers for Cdc7/Dbf4 activity.
  • To validate an in vitro to in vivo workflow for mapping kinase substrate phosphorylation sites.

Main Methods:

  • High-resolution mass spectrometry was employed to identify phosphorylation sites on MCM2.
  • In vitro kinase assays and analysis of cancer cell lines were used to confirm phosphorylation events.
  • Development and validation of phospho-specific antibodies (pS108 and pS40) for MCM2.

Main Results:

  • Six phosphorylation sites on human MCM2 were identified, with two previously undescribed.
  • Cdc7/Dbf4 was confirmed to mediate phosphorylation at serine 108 (S108) and serine 40 (S40) on MCM2.
  • Phospho-specific antibodies for pS108 and pS40 MCM2 were generated, serving as reliable indicators of Cdc7/Dbf4 activity.

Conclusions:

  • This study elucidates specific MCM2 phosphorylation events regulated by Cdc7/Dbf4, advancing the understanding of DNA replication initiation.
  • The developed phospho-specific antibodies offer valuable tools for monitoring Cdc7/Dbf4 kinase activity in cancer research and therapeutic development.
  • The presented workflow provides a generalizable method for identifying and validating phosphorylation sites on kinase substrates.

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