A MAJOR DNA-BINDING PROTEIN ENCODED BY BALF2 OPEN READING FRAME OF EPSTEIN-BARR-VIRUS (EBV) FORMS A COMPLEX WITH OTHER EBV DNA-BINDING PROTEINS - DNAASE, EA-D, AND DNA-POLYMERASE

A major 135-kDa DNA binding protein (mDBP) encoded by the BALF2 open r eading frame of Epstein-Barr Virus (EBV) is known to be an essential p rotein 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 replicatio n: DNA polymerase, EA-D (diffused early antigen), and DNAase. Immunopr ecipitation assays followed by mono-and two-dimensional electrophoresi s showed that mDBP forms a complex with these three DBP. Other complex es 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 p olymerase retained its activity in the complexed form with mDBP. Our r esults suggest that these complexes already present before DNA synthes is are necessary for EBV DNA synthesis. (C) 1997 Academic Press.