The Epstein-Barr virus replication protein BBLF2/3 provides an origin-tethering function through interaction with the zinc finger DNA binding protein ZBRK1 and the KAP-1 corepressor

J Virol. 2005 Jan;79(1):245-56. doi: 10.1128/JVI.79.1.245-256.2005.

Abstract

Herpesviruses encode a set of core proteins essential for lytic replication of their genomes. Three of these proteins form a tripartite helix-primase complex that, in the case of Epstein-Barr virus (EBV), consists of the helicase BBLF4, the primase BSLF1, and the linker protein BBLF2/3. BBLF2/3 and its homologs in the other herpesviruses remain relatively poorly characterized. To better understand the contribution to replication made by BBLF2/3, a yeast two-hybrid screen was performed with BBLF2/3 as the bait protein. This screen identified as interactors a number of cell replication-related proteins such as DNA polymerase beta and subunits of DNA polymerase delta along with the EBV-encoded DNase BGLF5. The screen also identified the DNA binding zinc finger protein ZBRK1 and the ZBRK1 corepressor KAP-1 as BBLF2/3 interactors. Interaction between BBLF2/3 and ZBRK1 and KAP-1 was confirmed in coimmunoprecipitation assays. A binding site for ZBRK1 in the EBV oriLyt enhancer was identified by electrophoretic mobility shift assay. ZBRK1, KAP-1, and the ZBRK1 binding protein BRCA1 were shown by indirect immunofluorescence to be present in replication compartments in lytically induced D98-HR1 cells, and additionally, chromatin immunoprecipitation assays determined that these proteins associated with oriLyt DNA. Replication of an oriLyt plasmid and a variant oriLyt (DeltaZBRK1) plasmid was examined in lytically induced D98-HR1 cells. Exogenous ZBRK1, KAP-1, or BRCA1 increased the efficiency of oriLyt replication, while deletion of the ZBRK1 binding site impaired replication. These experiments identify ZBRK1 as another cell protein that, through BBLF2/3, provides a tethering point on oriLyt for the EBV replication complex. The data also suggest that BBLF2/3 may serve as a contact interface for cell proteins involved in replication of EBV oriLyt.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Binding Sites
  • Cell Line
  • Chlorocebus aethiops
  • Chromatin Immunoprecipitation
  • DNA Replication
  • DNA-Binding Proteins / metabolism*
  • Gene Deletion
  • HeLa Cells
  • Herpesvirus 4, Human / genetics
  • Herpesvirus 4, Human / metabolism*
  • Herpesvirus 4, Human / physiology
  • Humans
  • Replication Origin / physiology*
  • Repressor Proteins / metabolism*
  • Tripartite Motif-Containing Protein 28
  • Two-Hybrid System Techniques
  • Vero Cells
  • Viral Proteins / genetics
  • Viral Proteins / metabolism*
  • Virus Replication

Substances

  • DNA-Binding Proteins
  • Repressor Proteins
  • Viral Proteins
  • ZNF350 protein, human
  • TRIM28 protein, human
  • Tripartite Motif-Containing Protein 28