End Processing in NHEJ by Polymerase λ and PNKP is coordinated during short-range synapsis

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Non-homologous end joining (NHEJ) is a critical DNA double-strand break (DSB) repair pathway.
• NHEJ utilizes accessory factors for end processing, including trimming overhangs and filling gaps.

Purpose of the Study:

• To investigate the molecular mechanisms of DNA end processing during NHEJ.
• To determine the structure of the NHEJ-specific polymerase Pol λ in complex with other repair factors.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was used to determine the structure of Pol λ bound to the short-range synaptic complex.
• Analysis of the coordinated activities of Pol λ and PNKP within the short-range synaptic complex.

Main Results:

• The cryo-EM structure revealed how Pol λ is recruited to the NHEJ complex and provided a model for its activity.
• Simultaneous binding of Pol λ and PNKP to the short-range synaptic complex demonstrated the formation of large, multifunctional repair complexes.

Conclusions:

• NHEJ employs large, multifunctional complexes for efficient DNA repair.
• Understanding Pol λ's role in NHEJ provides insights into DSB repair pathways and potential therapeutic targets.