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Trimeric structure of human proliferating cell nuclear antigen. Implications for enzymatic function and autoantibody
S R Brand1, R M Bernstein, M B Mathews
1Department of Rheumatology, University of Manchester, UK.
Journal of Immunology (Baltimore, Md. : 1950)
|October 1, 1994
Summary
Proliferating cell nuclear antigen (PCNA) functions as a trimeric ring in DNA replication. Autoantibodies in lupus target this native trimeric form, confirming its role in autoimmunity.
Area of Science:
- Molecular Biology
- Immunology
- Structural Biology
Background:
- Proliferating cell nuclear antigen (PCNA) is a key DNA replication factor.
- PCNA is a target for autoantibodies in systemic lupus erythematosus (SLE).
- PCNA autoantigenicity is conformation-dependent, requiring a nearly full-length molecule.
Purpose of the Study:
- To analyze the native structure and size of PCNA.
- To investigate the relationship between PCNA structure and autoantibody binding.
- To provide experimental support for PCNA's functional structure in DNA replication.
Main Methods:
- Gel filtration chromatography.
- Glycerol gradient sedimentation.
- Analysis of PCNA from various sources (HeLa cells, overexpressed in bacteria, wheat germ cell-free system) and mutant forms.
Main Results:
- Full-length PCNA consistently behaved as a trimer across different sources.
- A correlation was observed between the trimeric form of PCNA and binding to human anti-PCNA autoantibodies.
- Mutant protein analysis supported the specificity of autoantibodies for the native, active PCNA conformation.
Conclusions:
- PCNA functions as a trimer, likely forming a ring structure during DNA replication.
- Autoantibodies in SLE are specific for the native, trimeric form of PCNA.
- These findings support the hypothesis that autoantibodies arise in response to native antigens.