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DNA ligase I and proliferating cell nuclear antigen form a functional complex.
S Tom1, L A Henricksen, M S Park
1Department of Biochemistry and Biophysics, University of Rochester School of Medicine and Dentistry, 601 Elmwood Ave., Rochester, NY 14642, USA.
The Journal of Biological Chemistry
|May 2, 2001
Summary
Proliferating cell nuclear antigen (PCNA) significantly enhances DNA ligase I activity by improving its binding to DNA. This interaction is crucial for DNA replication and repair, with PCNA encircling DNA to stabilize DNA ligase I.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- DNA ligase I seals DNA nicks during replication and repair.
- DNA ligase I physically interacts with proliferating cell nuclear antigen (PCNA).
Purpose of the Study:
- To investigate how PCNA affects DNA ligase I activity.
- To elucidate the mechanism of PCNA-mediated enhancement of DNA ligase I.
Main Methods:
- In vitro enzyme activity assays.
- Electrophoretic mobility shift assays (EMSAs).
- Site-directed mutagenesis and DNA substrate modification.
Main Results:
- Human PCNA enhances human DNA ligase I reaction rates up to 5-fold.
- PCNA specifically stimulates DNA ligase I, not T4 DNA ligase.
- PCNA binding to DNA enhances DNA ligase I's affinity for ligation sites.
- PCNA must encircle duplex DNA to stimulate DNA ligase I, requiring loading by Replication Factor C.
Conclusions:
- PCNA stabilizes DNA ligase I association with nicked DNA duplexes.
- PCNA acts as a crucial factor for efficient DNA ligation in replication and repair pathways.