CBP and p300 acetylate PCNA to link its degradation with nucleotide excision repair synthesis

Area of Science:

• Molecular Biology
• Cellular Biology
• Biochemistry

Background:

• Proliferating cell nuclear antigen (PCNA) is vital for DNA transactions, acting as a platform for repair and replication factors.
• Maintaining genome stability requires preventing excessive PCNA retention on chromatin.
• Mechanisms regulating PCNA removal and degradation post-nucleotide excision repair (NER) remain unclear.

Purpose of the Study:

• To elucidate the mechanism of PCNA removal and degradation after DNA damage, specifically during NER.
• To identify the role of post-translational modifications in regulating PCNA fate after repair.

Main Methods:

• Investigated PCNA acetylation by CREB-binding protein (CBP) and p300 in vitro and in cells.
• Utilized site-directed mutagenesis to alter PCNA acetylation sites (Lys13,14,77,80).
• Assessed DNA replication and repair, UV sensitivity, and PCNA degradation in wild-type and mutant cells.
• Examined PCNA acetylation and degradation in CBP/p300 depleted cells and under proteasome inhibition.

Main Results:

• CBP and p300 acetylate PCNA at specific lysine residues (Lys13,14,77,80), promoting its removal and degradation during NER.
• Mutations at these acetylation sites impaired DNA replication/repair, increased UV sensitivity, and blocked PCNA degradation.
• Depletion of CBP/p300 or impaired PCNA loading prevented acetylation and degradation.
• Proteasome inhibition led to the accumulation of acetylated PCNA.

Conclusions:

• A novel CBP/p300-dependent acetylation mechanism regulates PCNA removal and degradation after DNA damage.
• This process links DNA repair synthesis to PCNA clearance, ensuring genome stability.
• Acetylation of PCNA by CBP/p300 is essential for efficient DNA repair and preventing genomic instability.