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Mol. Cell. Biol., May 1997, 2756-2763, Vol 17, No. 5
BL Black, J Lu and EN Olson
Myocyte enhancer factor 2 (MEF2) proteins serve as important muscle
transcription factors. In addition, MEF2 proteins have been shown to
potentiate the activity of other cell-type-specific transcription factors
found in muscle and brain tissue. While transcripts for MEF2 factors are
widely expressed in a variety of cells and tissues, MEF2 proteins and
binding activity are largely restricted to skeletal, smooth, and cardiac
muscle and to brain. This disparity between MEF2 protein and mRNA
expression suggests that translational control may play an important role
in regulating MEF2 expression. In an effort to identify sequences within
the MEF2A message which control translation, we isolated the mouse MEF2A 3'
untranslated region (UTR) and fused it to the chloramphenicol
acetyltransferase (CAT) reporter gene. Here, we show by CAT assay that the
MEF2A 3' UTR dramatically inhibits CAT gene expression in vivo and that
this inhibition is due to an internal region within the highly conserved 3'
UTR. RNase protection analyses demonstrated that the steady-state level of
CAT mRNA produced in vivo was not affected by fusion of the MEF2A 3' UTR,
indicating that the inhibition of CAT activity resulted from translational
repression. Furthermore, fusion of the MEF2A 3' UTR to CAT inhibited
translation in vitro in rabbit reticulocyte lysates. We also show that the
translational repression mediated by the 3' UTR of MEF2A is regulated
during muscle cell differentiation. As muscle cells in culture
differentiate, the translational inhibition caused by the MEF2A 3' UTR is
relaxed. These results demonstrate that the MEF2A 3' UTR functions as a
cis-acting translational repressor both in vitro and in vivo and suggest
that this repression may contribute to the tissue-restricted expression and
binding activity of MEF2A.
Copyright © 1997, American Society for Microbiology
The MEF2A 3' untranslated region functions as a cis-acting translational repressor
Department of Molecular Biology and Oncology, The University of Texas Southwestern Medical Center, Dallas 75235, USA.
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