Send to:

Choose Destination
See comment in PubMed Commons below
J Virol. 2007 Aug;81(16):8451-67. Epub 2007 May 30.

Direct interactions of Kaposi's sarcoma-associated herpesvirus/human herpesvirus 8 ORF50/Rta protein with the cellular protein octamer-1 and DNA are critical for specifying transactivation of a delayed-early promoter and stimulating viral reactivation.

Author information

  • 1Department of Microbiology and Molecular Genetics, University of Medicine and Dentistry of New Jersey/New Jersey Medical School, 225 Warren Street, Newark, NJ 07103, USA.


The Kaposi's sarcoma-associated herpesvirus (KSHV) delayed-early K-bZIP promoter contains an ORF50/Rta binding site whose sequence is conserved with the ORF57 promoter. Mutation of the site in the full-length K-bZIP promoter reduced Rta-mediated transactivation by greater than 80%. The K-bZIP element contains an octamer (Oct) binding site that overlaps the Rta site and is well conserved with Oct elements found in the immediate-early promoters of herpes simplex virus type 1(HSV-1). The cellular protein Oct-1, but not Oct-2, binds to the K-bZIP element in a sequence-specific fashion in vitro and in vivo and stimulates Rta binding to the promoter DNA. The coexpression of Oct-1 enhances Rta-mediated transactivation of the wild type but not the mutant K-bZIP promoter, and Oct-1 and Rta proteins bind to each other directly in vitro. Mutations of Rta within an amino acid sequence conserved with HSV-1 virion protein 16 eliminate Rta's interactions with Oct-1 and K-bZIP promoter DNA but not RBP-Jk. The binding of Rta to both Oct-1 and DNA contributes to the transactivation of the K-bZIP promoter and viral reactivation, and Rta mutants deficient for both interactions are completely debilitated. Our data suggest that the Rta/Oct-1 interaction is essential for optimal KSHV reactivation. Transfections of mouse embryo fibroblasts and an endothelial cell line suggest cell-specific differences in the requirement for Oct-1 or RBP-Jk in Rta-mediated transactivation of the K-bZIP promoter. We propose a model in which Rta transactivation of the promoter is specified by the combination of DNA binding and interactions with several cellular DNA binding proteins including Oct-1.

[PubMed - indexed for MEDLINE]
Free PMC Article
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire Icon for PubMed Central
    Loading ...
    Write to the Help Desk