Related Experiment Video
Updated: Jul 6, 2026

Identification of Cyclin-dependent Kinase 1 Specific Phosphorylation Sites by an In Vitro Kinase Assay
Published on: May 3, 2018
Claspin is phosphorylated in the Chk1-binding domain by a kinase distinct from Chk1
Lara N Bennett1, Conor Larkin, David A Gillespie
1Biomedical Research Centre, Level 5, College of Medicine Dentistry and Nursing, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, Scotland, UK.
Abstract:
Chk1 protein kinase plays a critical role in checkpoints that restrict progression through the cell cycle if DNA replication has not been completed or DNA damage has been sustained. ATR-dependent activation of Chk1 is mediated by Claspin. Phosphorylation of Claspin at two sites (Thr916 and Ser945 in humans) in response to DNA replication arrest or DNA damage recruits Chk1 to Claspin. Chk1 is subsequently phosphorylated by ATR and fully activated to control cell cycle progression. We show that ablation of Chk1 by siRNA in human cells or its genetic deletion in chicken DT40 cells does not prevent phosphorylation of Claspin at Thr916 (Ser911 in chicken). Chk1, however, does play other roles, possibly indirect, in the phosphorylation of Claspin and its induction. These results demonstrate that phosphorylation of Claspin within the Chk1-binding domain is catalysed by an ATR-dependent kinase distinct from Chk1.
More Related Videos
Related Concept Videos
Cytoskeletal Linker Proteins - Plakins
The JAK-STAT Signaling Pathway
Calmodulin-dependent Signaling
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
The Spindle Assembly Checkpoint
Many proteins function together to control the spindle assembly checkpoint. Mutations affecting these proteins may allow cells to proceed into anaphase prematurely, resulting in the...
Amplifying Signals via Enzymatic Cascade
Protein Kinases and Phosphatases
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...

