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J. Virol., May 1996, 3051-3059, Vol 70, No. 5
WJ Bowers, LA Baglia and A Ruddel
The avian leukosis and sarcoma virus long terminal repeat (LTR) enhancers
feature directly repeated CCAAT/enhancer element sequences which are also
found in many viral and cellular gene enhancers. While most members of the
CCAAT/enhancer element-binding protein (C/EBP) transcription factor family
exhibit tissue-restricted expression, there may be ubiquitously expressed
C/EBP-like factors that regulate widespread CCAAT/enhancer element-driven
transcription. An avian C/EBP- related factor designated Al/EBP was previ-
ously shown to bind CCAAT/enhancer elements within the avian leukosis virus
(ALV) and Rous sarcoma virus (RSV) LTR enhancers in a pattern identical to
that of a B- cell LTR-binding factor (W. J. Bowers and A. Ruddell, J.
Virol. 66:6578- 6586, 1992). An Al/EBP-specific antiserum recognizes a
40-kDa LTR CCAAT/enhancer element-binding protein purified from avian B
lymphoma cells. A1/EBP is widely expressed at the mRNA and protein levels,
suggesting that this protein could be important not only in regulating
widespread expression of the AIN and RSV retroviruses but also in
controlling the expression of other viral and cellular gene enhancers that
possess CCAAT/enhancer motifs. We also found that an NF-KB/Rel- related
protein is a component of the LTR CCAAT/enhancer element binding complex
through its interaction with A1/EBP. At least one of the NF-kappaB family
members, p65 (RelA), is capable of activating LTR CCAAT/enhancer
element-driven transcription. These findings suggest a role for Rel-related
factors in the regulation of AIN or RSV LTR-driven transcription via an
interaction with Al/EBP.
Copyright © 1996, American Society for Microbiology
Regulation of avian leukosis virus long terminal repeat-enhanced transcription by C/EBP-Rel interactions
Department of Microbiology and Immunology, University of Rochester, New York 14642, USA.
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