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A major DNA binding protein encoded by BALF2 open reading frame of Epstein-Barr virus (EBV) forms a complex with
Y Zeng1, J Middeldorp, J J Madjar
1Laboratoire du Virologie Moléculaire, IVMC, UMR5537, CNRS, Faculté de Médecine R.T.H. Laënnec, Lyon, France.
Abstract:
A major 135-kDa DNA binding protein (mDBP) encoded by the BALF2 open reading frame of Epstein-Barr Virus (EBV) is known to be an essential protein for the induction of the lytic cycle. The present investigation was carried out to know whether this protein forms a complex in vivo with other viral DNA binding proteins (DBP) involved in DNA replication: DNA polymerase, EA-D (diffused early antigen), and DNAase. Immunoprecipitation assays followed by mono- and two-dimensional electrophoresis showed that mDBP forms a complex with these three DBP. Other complexes were also found such as EA-D/DNAase, DNA polymerase/DNAase, and DNA polymerase/EA-D. The complexed forms already exist in the early stage of EBV cycle before DNA synthesis is induced in the EBV producer P3HR-1 cell line. The exonuclease activity encoded by DNAase was found to be inhibited when this enzyme complexed with mDBP, while the EBV DNA polymerase retained its activity in the complexed form with mDBP. Our results suggest that these complexes already present before DNA synthesis are necessary for EBV DNA synthesis.
Insights
Epstein-Barr Virus (EBV) DNA binding protein (mDBP) forms complexes with viral proteins essential for DNA replication. These pre-replication complexes, including EBV DNA polymerase, are crucial for initiating the EBV lytic cycle.
Area of Science:
- Virology
- Molecular Biology
- Epigenetics
Background:
- Epstein-Barr Virus (EBV) DNA binding protein (mDBP), encoded by BALF2, is vital for initiating the lytic cycle.
- Understanding protein interactions is key to elucidating EBV replication mechanisms.
Purpose of the Study:
- To investigate in vivo complex formation of EBV mDBP with other viral DNA binding proteins (DBP) involved in DNA replication.
- To determine the functional impact of these complex formations on viral DNA synthesis.
Main Methods:
- Immunoprecipitation assays.
- Mono- and two-dimensional electrophoresis.
- Analysis of enzyme activity within protein complexes.
Main Results:
- EBV mDBP forms in vivo complexes with viral DNA polymerase, EA-D (diffused early antigen), and DNAase.
- Additional complexes observed include EA-D/DNAase, DNA polymerase/DNAase, and DNA polymerase/EA-D.
- These complexes pre-exist the onset of DNA synthesis in EBV-producing cells.
- EBV DNA polymerase activity is retained within its complex, while DNAase activity is inhibited when complexed with mDBP.
Conclusions:
- The identified protein complexes, present early in the EBV cycle, are essential for initiating EBV DNA synthesis.
- Complex formation regulates the activity of key viral enzymes, suggesting a coordinated mechanism for replication initiation.