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A specific 3' exonuclease activity of UvrABC
1Yale University School of Medicine, Department of Therapeutic Radiology, New Haven, CT 06520-8040, USA.
The EMBO Journal
|February 28, 1998
Summary
The UvrABC nuclease exhibits specific cutting of undamaged DNA, revealing a novel ABC 3' exonuclease activity. This activity, distinct from dual incision, aids in DNA repair gap formation for complex lesions.
Area of Science:
- Molecular Biology
- DNA Repair Mechanisms
- Enzymology
Background:
- The UvrABC nuclease is central to DNA repair, primarily known for dual incision at DNA damage sites.
- Understanding the nuclease's activity on undamaged DNA is crucial for a complete picture of DNA repair pathways.
Purpose of the Study:
- To investigate the specific cutting activity of UvrABC nuclease on undamaged DNA.
- To characterize a potential exonuclease activity of UvrABC and its role in DNA repair.
Main Methods:
- Incubation of UvrABC nuclease with undamaged M13 DNA circles and DNA duplexes containing AAF adducts.
- Analysis of DNA cleavage products to identify cut sites and characterize nuclease activity.
Main Results:
- UvrABC nuclease specifically cuts undamaged DNA at 7-nucleotide intervals from the 3' terminus.
- This activity, termed ABC 3' exonuclease, is distinct from the dual incision mechanism.
- Additional cuts were observed on damaged DNA, suggesting the involvement of ABC 3' exonuclease activity.
Conclusions:
- The UvrABC nuclease possesses a 3' exonuclease activity on undamaged DNA, separate from its role in dual incision.
- This ABC 3' exonuclease activity may facilitate gap formation for RecA-mediated repair of complex DNA lesions.
- The activity's dependence on higher protein concentrations suggests relevance during SOS response and increased UvrA/UvrB levels.