Human DNA-dependent protein kinase activation mechanism

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• DNA-dependent protein kinase (DNA-PK) is crucial for DNA damage response and repair in humans.
• The DNA-PK complex consists of the catalytic subunit and the Ku70/80 heterodimer, requiring DNA for its function.

Purpose of the Study:

• To elucidate the molecular mechanisms regulating human DNA-PK complex activation.
• To understand the role of ligand binding and specific protein domains in DNA-PK kinase activity.

Main Methods:

• Utilized a DNA-PK-selective inhibitor (M3814).
• Determined two cryo-electron microscopy (cryo-EM) structures of the human DNA-PK complex (intermediate and active states).

Main Results:

• Identified conformational changes in DNA-PK upon ligand binding and interaction with its string region (residues 802-846), including the helix-hairpin-helix motif (residues 816-836).
• Demonstrated the regulatory role of the ligand and the DNA-binding motif in kinase activation.
• Highlighted the contribution of protein-protein interactions and flexible regions to kinase modulation.

Conclusions:

• Ligand binding and specific DNA-interacting regions are key regulators of DNA-PK activation.
• The findings explain the DNA-dependent nature of DNA-PK.
• Provides enhanced molecular insights into DNA-PK catalysis and its role in DNA repair.