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Molecular and Cellular Biology, December 2001, p. 8490-8503, Vol. 21, No. 24
Section on Molecular Neurobiology, National
Institute of Child Health and Human Development, National
Institutes of Health, Bethesda, Maryland 20892
Received 1 May 2001/Returned for modification 25 June 2001/Accepted 18 September 2001
Transcription is a major regulatory mechanism for the generation of
slow- and fast-twitch myofibers. We previously identified an upstream
region of the slow TnI gene (slow upstream regulatory element [SURE])
and an intronic region of the fast TnI gene (fast intronic regulatory
element [FIRE]) that are sufficient to direct fiber type-specific
transcription in transgenic mice. Here we demonstrate that the
downstream half of TnI SURE, containing E box, NFAT, MEF-2, and CACC
motifs, is sufficient to confer pan-skeletal muscle-specific expression
in transgenic mice. However, upstream regions of SURE and FIRE are
required for slow and fast fiber type specificity, respectively. By
adding back upstream SURE sequences to the pan-muscle-specific
enhancer, we delineated a 15-bp region necessary for slow muscle
specificity. Using this sequence in a yeast one-hybrid screen, we
isolated cDNAs for general transcription factor 3 (GTF3)/muscle TFII-I
repeat domain-containing protein 1 (MusTRD1). GTF3 is a multidomain
nuclear protein related to initiator element-binding transcription
factor TF II-I; the genes for both proteins are deleted in persons with
Williams-Beuren syndrome, who often manifest muscle weakness. Gel
retardation assays revealed that full-length GTF3, as well as its
carboxy-terminal half, specifically bind the bicoid-like
motif of SURE (GTTAATCCG). GTF3 expression is neither muscle
nor fiber type specific. Its levels are highest during a period of
fetal development that coincides with the emergence of specific fiber
types and transiently increases in regenerating muscles damaged by
bupivacaine. We further show that transcription from TnI SURE is
repressed by GTF3 when overexpressed in electroporated adult soleus
muscles. These results suggest a role for GTF3 as a regulator of slow
TnI expression during early stages of muscle development and suggest
how it could contribute to Williams-Beuren syndrome.
0270-7306/01/$04.00+0 DOI: 10.1128/MCB.21.24.8490-8503.2001
Molecular Dissection of DNA Sequences and Factors
Involved in Slow Muscle-Specific Transcription


*
Corresponding author. Mailing address: Section on
Molecular Neurobiology, National Institute of Child Health and Human
Development, National Institutes of Health, Bethesda, MD 20892. Phone:
(301) 496-3298. Fax: (301) 496-9939. E-mail:
buonanno{at}helix.nih.gov.
Present address: Universidad de Castilla la Mancha, Facultad de
Medicina, Albacete 02071, Spain.
Present address: National Center for Biotechnology Information,
NIH, Bethesda, MD 20894.
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