Poly(ADP-ribose)-binding promotes Exo1 damage recruitment and suppresses its nuclease activities

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• Exonuclease 1 (Exo1) is crucial for DNA repair, genome stability, and cancer suppression.
• The precise regulatory mechanisms governing Exo1 activity remain largely unknown.

Purpose of the Study:

• To elucidate the regulatory mechanisms controlling Exonuclease 1 (Exo1) activity.
• To investigate the role of poly(ADP-ribose) (PAR) and other interacting proteins in Exo1 function.

Main Methods:

• Protein interaction studies to identify binding partners of Exo1.
• Biochemical assays to assess Exo1 enzymatic activity in response to regulatory factors.
• Cellular assays to evaluate Exo1 recruitment and DNA repair dynamics.

Main Results:

• Exo1 directly interacts with poly(ADP-ribose) (PAR), a posttranslational modification at DNA damage sites.
• PAR binding promotes Exo1 recruitment to DNA damage sites, facilitated by PCNA interaction.
• 14-3-3 proteins antagonize PAR and PCNA effects on Exo1, modulating its association.
• PAR binding inhibits Exo1's exonuclease and 5' flap endonuclease activities, but PAR synthesis blockade doesn't overtly affect DNA resection in vitro.

Conclusions:

• PAR acts as a key regulator of Exo1, influencing its localization and enzymatic function.
• The interplay between PAR, PCNA, and 14-3-3 proteins fine-tunes Exo1 activity for proper DNA damage response.
• These findings provide insights into how Exo1 balances DNA end resection and prevents aberrant DNA break processing.