LC8/DYNLL1 is a 53BP1 effector and regulates checkpoint activation

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• The tumor suppressor protein 53BP1 is a critical scaffold protein in DNA double-strand break (DSB) repair.
• 53BP1 orchestrates DNA damage response (DDR) factors for checkpoint activation and non-homologous end joining (NHEJ).

Purpose of the Study:

• To identify novel effectors of 53BP1 in the DNA damage response.
• To investigate the role of LC8 (DYNLL1) as a 53BP1 effector.

Main Methods:

• Utilized laser-induced DNA damage to observe protein recruitment.
• Employed genetic inactivation of LC8 and its interaction with 53BP1.
• Assessed cellular sensitivity to ionizing radiation and PARP inhibition in BRCA1-depleted cells.

Main Results:

• LC8 (DYNLL1) accumulates at DNA damage sites in a 53BP1-dependent manner, requiring the H2AX-MDC1-RNF8-RNF168 pathway.
• Genetic inactivation of LC8 or its interaction with 53BP1 led to DNA damage checkpoint defects.
• Loss of LC8 mitigated the hypersensitivity of BRCA1-deficient cells to ionizing radiation and PARP inhibitors.

Conclusions:

• LC8 (DYNLL1) is identified as a key effector of 53BP1 in mediating specific DSB responses.
• The 53BP1-LC8 module plays a role in counteracting BRCA1-dependent functions within the DDR.
• These findings elucidate a novel pathway in DNA repair and genome stability.