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Mol. Cell. Biol., 07 1997, 3527-3535, Vol 17, No. 7
BS Nikolajczyk, M Cortes, R Feinman and R Sen
A tripartite domain of the immunoglobulin mu heavy-chain gene enhancer that
activates transcription in B cells contains binding sites for PU.1, Ets-1,
and a leucine zipper-containing basic helix-loop-helix factor. Because PU.1
is expressed only in B cells and macrophages, we tested the activity of a
minimal mu enhancer fragment in macrophages by transient transfections. The
minimal mu enhancer activated transcription in macrophages, and the
activity was dependent on all three sites. Analysis of mutated enhancers,
in which spacing and orientation of the ETS protein binding sites had been
changed, suggested that the mechanisms of enhancer activation were
different in B cells and macrophages. Thus, ETS protein binding sites may
be combined in different ways to generate tissue-specific transcription
activators. Despite the activity of the minimal enhancer in macrophages, a
larger mu enhancer fragment was inactive in these cells. We propose that
formation of the nucleoprotein complex that is formed on the minimal
enhancer in macrophages cannot be helped by the neighboring muE elements
that are essential for activity of the monomeric enhancer.
Copyright © 1997, American Society for Microbiology
Combinatorial determinants of tissue-specific transcription in B cells and macrophages
Department of Biology, Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02254, USA.
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