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Modulation of RecA nucleoprotein function by the mutagenic UmuD'C protein complex
W M Rehrauer1, I Bruck, R Woodgate
1Division of Biological Sciences, Sections of Microbiology and of Molecular and Cellular Biology, University of California, Davis, California 95616-8665, USA.
The Journal of Biological Chemistry
|November 26, 1998
Summary
The Umu(D')2C complex inhibits the DNA repair function of RecA protein, shifting its role from error-free repair to error-prone DNA replication. This binding mechanism is crucial for mutagenic repair pathways.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- RecA, UmuC, and UmuD' proteins are vital for DNA lesion bypass.
- RecA protein typically facilitates homologous DNA pairing for repair.
Purpose of the Study:
- To investigate the interaction between the Umu(Dackslash')2C complex and RecA protein.
- To elucidate the mechanism by which Umu(Dackslash')2C modulates RecA's function in DNA repair.
Main Methods:
- Utilized biosensor measurements to quantify Umu(Dackslash')2C binding to RecA nucleoprotein filaments.
- Assessed the impact of Umu(Dackslash')2C on RecA's LexA repressor cleavage and ATPase activity.
Main Results:
- Purified Umu(Dackslash')2C complex was shown to inhibit RecA's recombination function.
- Umu(Dackslash')2C binds to the RecA nucleoprotein filament at a 1:2 stoichiometry (Umu(Dackslash')2C:RecA).
- Umu(Dackslash')2C competitively inhibits LexA cleavage but not RecA ATPase activity, indicating binding near the helical groove.
Conclusions:
- Umu(Dackslash')2C binding impedes RecA-mediated DNA pairing and recombination.
- This interaction restricts RecA's normal genomic maintenance role, redirecting it towards mutagenic repair.
- The Umu(Dackslash')2C modulation of RecA is a key step in transitioning to error-prone DNA replication.