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The Epstein-Barr virus polymerase accessory factor BMRF1 adopts a ring-shaped structure as visualized by electron
Alexander M Makhov1, Deepa Subramanian, Elizabeth Holley-Guthrie
1Department of Microbiology and Immunology, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599-7295, USA.
The Journal of Biological Chemistry
|August 3, 2004
Summary
Epstein-Barr virus (EBV) BMRF1 protein forms large, ring-shaped structures, unlike other viral polymerase accessory factors. This finding reveals a novel oligomeric state for viral replication machinery in human cells.
Area of Science:
- Virology
- Molecular Biology
- Structural Biology
Background:
- Epstein-Barr virus (EBV) utilizes core replication factors during lytic infection.
- The BMRF1 gene product functions as both a polymerase accessory factor and a transcription factor.
- The oligomeric state of BMRF1 and its potential to form ring structures were previously unknown.
Purpose of the Study:
- To investigate the oligomeric state and structure of the EBV BMRF1 protein.
- To determine if BMRF1 forms ring-shaped structures similar to other polymerase accessory factors.
Main Methods:
- Purification of BMRF1 from human cells infected with an adenovirus vector.
- Negative staining electron microscopy to visualize the protein structure.
Main Results:
- Purified BMRF1 formed large, flat, ring-shaped molecules (15.5 nm diameter) with a central hole (5.3 nm).
- The ring structure is consistent with a hexamer, larger than known trimeric sliding clamps.
- BMRF1 demonstrated self-association in solution, unlike some homologs.
Conclusions:
- EBV BMRF1 adopts a hexameric ring structure, extending the known diversity of polymerase accessory factor structures.
- This larger ring structure may have implications for EBV DNA replication and viral gene regulation.