Identification of a chaperone-code responsible for Rad51-mediated genome repair.

Area of Science:

• Molecular Biology
• Cellular Biology
• Biochemistry

Background:

• Posttranslational modifications, specifically acetylation, regulate the in vivo chaperone functions of Hsp90.
• The acetylation-deacetylation dynamics of Hsp90 are critical for various cellular processes.
• Rad51 is a key protein involved in DNA repair mechanisms in eukaryotes.

Purpose of the Study:

• To investigate the role of lysine acetylation of Hsp82 (a form of Hsp90) in DNA repair mediated by Rad51.
• To elucidate the mechanism by which Hsp82 acetylation influences the formation of functional complexes involved in DNA repair.

Main Methods:

• Site-directed mutagenesis to create Hsp82 lysine mutants (K27Q/K27R).
• Analysis of complex formation between Hsp82, Aha1, and Rad51 under different acetylation conditions.
• Epistasis analysis using hda1Δ (deacetylase deletion) mutants to assess the functional significance of Hsp82 acetylation.

Main Results:

• The acetylation status of Hsp82, particularly at lysine 27, is a major determinant in Rad51-mediated DNA repair.
• Deacetylation of Hsp82 at lysine 27 is essential for the formation of the Hsp82-Aha1-Rad51 complex, which is critical for client maturation.
• Formation of the Aha1-Rad51 complex is independent of Hsp82 and its acetylation status, suggesting it precedes Hsp82 interaction.
• Hsp82 K27Q/K27R mutants exhibit DNA damage sensitivity that is epistatic to the loss of the deacetylase Hda1, confirming the importance of reversible Hsp82 acetylation at K27.

Conclusions:

• The study highlights a specific Hsp82 chaperone modification code (acetylation at K27) and its interplay with cochaperones (Aha1) in a client-specific manner (Rad51) for DNA repair.
• The Hda1-Hsp90 axis represents a potential therapeutic target for cancer treatment, given the role of Rad51 in DNA repair in cancer cells.