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Replication protein A-directed unloading of PCNA by the Ctf18 cohesion establishment complex
Göran O Bylund1, Peter M J Burgers
1Department of Biochemistry, Washington University School of Medicine, 660 S. Euclid, St. Louis, Missouri 63110, USA.
Molecular and Cellular Biology
|June 21, 2005
Summary
A novel Ctf18-RFC complex efficiently unloads the DNA clamp PCNA, requiring ATP hydrolysis. This complex separates roles in sister chromatid cohesion and DNA replication clamp unloading.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Proliferating Cell Nuclear Antigen (PCNA) is crucial for DNA replication and repair, loaded by Replication Factor C (RFC).
- Regulated PCNA unloading is essential for replication termination, potentially involving additional factors.
Purpose of the Study:
- To identify factors involved in the regulated unloading of PCNA.
- To characterize the function of the Ctf18-RFC complex in PCNA dynamics.
Main Methods:
- Biochemical assays to test PCNA loading and unloading by various complexes.
- In vitro studies using purified proteins and DNA substrates.
- Analysis of subunit contributions within the Ctf18-RFC complex.
Main Results:
- The seven-subunit Ctf18-RFC complex efficiently unloads PCNA in an ATP-dependent manner.
- Ctf18-RFC also weakly loads PCNA onto naked DNA but unloading predominates on RPA-coated DNA.
- Other RFC complexes, including Rad24-RFC and Elg1-RFC, did not significantly unload PCNA.
Conclusions:
- The Ctf18-RFC complex acts as a specific PCNA unloader, distinct from its role in sister chromatid cohesion.
- This finding reveals a novel mechanism for regulating PCNA activity during DNA replication and repair.