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J. Virol., Jan 1997, 354-361, Vol 71, No. 1
C Nonkwelo, IK Ruf and J Sample
Expression of the Epstein-Barr virus (EBV) EBNA-1 protein within EBV-
positive tumor cells and subpopulations of latently infected B lymphocytes
in vivo is mediated by the promoter Qp. Previous studies have established
that Qp is a TATA-less promoter whose activation requires only proximal
regulatory elements and that it is negatively autoregulated through two
EBNA-1 binding sites downstream of the transcription initiation sites. The
objective of this study was to better define the properties of an essential
positive regulatory element (QRE-2) adjacent to a major transcription start
site of Qp and to evaluate the contributions of other potential regulatory
elements proximal to the Qp start site. Using DNA affinity purification and
UV cross-linking, we have identified the QRE-2-binding protein as a single
polypeptide of approximately 40 kDa. The DNA-binding properties of this
protein are clearly distinct from those of the TATA-binding protein,
suggesting that in the absence of a TATA box, QRE-2 may function as an
initiator element to direct assembly of TFIID near the transcription start
site. Mutational analysis of potential regulatory elements, furthermore,
indicated that the putative E2F binding sites within the EBNA-1 binding
domain can exert a positive influence on Qp that is EBNA- 1 independent,
suggesting that these regulatory elements play an additional if not
different role in Qp regulation than previously proposed. A model for the
regulation of Qp consistent with the current and previous findings which
provides for a simple but efficient mechanism of ensuring the EBNA-1
expression necessary to sustain long- term latency is presented.
Copyright © 1997, American Society for Microbiology
The Epstein-Barr virus EBNA-1 promoter Qp requires an initiator-like element
Department of Virology and Molecular Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
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