UBA domains mediate protein-protein interactions between two DNA damage-inducible proteins

Area of Science:

• Molecular and Cellular Biology
• Genetics and Genomics
• Biochemistry

Background:

• Pds1 is a critical regulator of anaphase in Saccharomyces cerevisiae, controlling cell cycle progression through mitosis.
• Pds1 degradation via the ubiquitin-proteasome pathway is essential for the metaphase-anaphase transition.
• Mutations in PDS1 can lead to cell cycle arrest and temperature-sensitivity.

Purpose of the Study:

• To identify genes that can suppress the temperature-sensitive phenotype of a mutant PDS1 allele in Saccharomyces cerevisiae.
• To investigate the role of the UBA domain in the function of Rad23 and Ddi1 proteins in PDS1 suppression.
• To elucidate the mechanism by which Rad23 and Ddi1 regulate cell division.

Main Methods:

• Functional screening for multicopy suppressors of a temperature-sensitive pds1 mutant.
• Analysis of gene function through genetic manipulation and phenotypic observation.
• Biochemical assays to study protein-protein interactions (dimerization) and ubiquitin binding.

Main Results:

• RAD23 and DDI1 were identified as multicopy suppressors of the pds1 temperature-sensitivity.
• The UBA domain, common to Rad23 and Ddi1, is essential for their PDS1 suppression activity.
• UBA domains mediate Rad23 homodimerization and Rad23-Ddi1 heterodimerization, and bind ubiquitin; Rad23 dimerization inhibits ubiquitin binding.

Conclusions:

• Rad23 and Ddi1 function in regulating cell division, likely through mechanisms involving the UBA domain.
• The UBA domain plays a key role in mediating protein interactions and ubiquitin binding, suggesting a regulatory switch.
• These findings propose a novel mechanism for regulating Rad23 and Ddi1 function in the context of cell cycle control.