Characterisation of the interaction between PCNA and Gadd45

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Proliferating Cell Nuclear Antigen (PCNA) is crucial for DNA replication and repair.
• Growth Arrest and DNA Damage (Gadd45) proteins are involved in cellular responses to DNA damage.
• Understanding the interaction between PCNA and Gadd45 is key to elucidating DNA repair mechanisms.

Purpose of the Study:

• To investigate the molecular interaction between PCNA and Gadd45.
• To map the specific regions of PCNA and Gadd45 involved in their binding.
• To determine the stoichiometry of the PCNA-Gadd45 complex.

Main Methods:

• Co-immunoprecipitation assays using specific antibodies.
• Yeast two-hybrid assays to confirm protein-protein interactions.
• Peptide ELISA and deletion analysis to map binding sites.
• Analysis of PCNA crystal structure.

Main Results:

• Confirmed interaction between human Gadd45 and both human and S. pombe PCNA.
• Identified the N-terminal 94 amino acids of Gadd45 as the PCNA-binding domain.
• Mapped two potential Gadd45 binding sites on PCNA, with the C-terminal 6 amino acids being critical.
• Gadd45 binds strongly to PCNA regions 1-20, 61-80, and 196-215.

Conclusions:

• PCNA and Gadd45 interact, with defined binding regions on both proteins.
• The interaction involves specific PCNA residues and the N-terminus of Gadd45.
• A potential stoichiometry of 2 Gadd45 molecules per PCNA monomer was suggested.
• These findings support a role for PCNA-Gadd45 complexes in coordinating cell cycle progression and DNA repair.