Structural basis for recruitment of the CHK1 DNA damage kinase by the CLASPIN scaffold protein

Area of Science:

• Molecular Biology
• Cellular Biology
• Biochemistry

Background:

• Checkpoint kinase 1 (CHK1) is vital for DNA damage checkpoints and cell survival during replicative stress.
• CHK1 is a significant target in anti-cancer drug discovery due to its role in cellular response to DNA damage.
• Activation of CHK1 by ATR involves interaction with CLASPIN, an intrinsically disordered protein.

Purpose of the Study:

• To determine the crystal structure of the CHK1 kinase domain bound to a CLASPIN motif.
• To elucidate the molecular mechanism of CHK1 activation by CLASPIN.

Main Methods:

• X-ray crystallography was used to determine the structure of the CHK1 kinase domain complexed with a CLASPIN motif.
• Biochemical assays were performed to assess the phosphorylation status of the CLASPIN motif and its effect on substrate phosphorylation.

Main Results:

• The crystal structure reveals that the CLASPIN motif binds to a conserved site on CHK1 near the substrate-binding cleft.
• This binding site is adjacent to the phosphate-sensing region in other kinases.
• The CLASPIN motif is not phosphorylated by CHK1 and does not influence the phosphorylation of a CDC25 substrate peptide.

Conclusions:

• CLASPIN functions as a scaffold protein, facilitating CHK1 activation by ATR through a non-phosphorylative interaction.
• The structural data provides insights into the mechanism of CHK1 activation, potentially guiding the development of CHK1-targeting cancer therapies.