Uncovering nick DNA binding by LIG1 at the single-molecule level

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• DNA strand breaks are continuous threats to genome stability, potentially causing lethal double-strand breaks, deletions, and duplications.
• DNA ligase 1 (LIG1) is essential for joining Okazaki fragments during replication and sealing nicks in DNA repair pathways.
• The mechanism by which LIG1 recognizes its DNA substrate has remained largely unknown.

Approach:

• Utilized single-molecule techniques to investigate the dynamics of LIG1 binding to nicked DNA.
• Compared the binding behavior of full-length LIG1 with its C-terminal domain.
• Analyzed the role of the N-terminal non-catalytic region in LIG1's DNA interaction.

Key Points:

• LIG1 exhibits both specific and non-specific binding to double-stranded DNA (dsDNA).
• LIG1 displays diffusive behavior, ultimately forming stable complexes at DNA nicks.
• The N-terminal region of LIG1 enhances binding at nick sites and promotes 1D diffusion for efficient searching.

Conclusions:

• This study provides novel single-molecule insights into how LIG1 recognizes and binds to DNA nicks.
• The N-terminal domain is critical for LIG1's efficient nick search and binding.
• Understanding LIG1's substrate recognition is vital for comprehending DNA repair and maintaining genome integrity.