Cis- and trans-acting factors regulating transcription of the bgt1
gene in response to hypertonicity.
Miyakawa, Hiroshi, Seung Kyoon Woo, Ching-Pu Chen, Stephen C. Dahl,
Joseph S. Handler, and H. Moo Kwon.
Division of Nephrology, The Johns Hopkins School of Medicine, 963
Ross Building, 720 Rutland Avenue, Baltimore, Maryland 21205
APStracts 5:0020F, 1998.
We have previously identified a tonicity-responsive enhancer (TonE) in
the promoter region of the canine BGT1 gene. TonE mediates
hypertonicity-induced stimulation of transcription. Here we
characterize TonE and TonE binding proteins (TonEBPs) to provide a
biochemical basis for cloning of the TonEBPs. Mutational analysis
applied to both hypertonicity-induced stimulation of transcription
and TonEBP binding reveals that TonE is 11 base pairs in length with
the consensus sequence of (C/T)GGAAnnn(C/T)n(C/T). Activity of the
TonEBPs increases in response to hypertonicity with a time course
similar to that of transcription of the BGT1 gene. Studies with
inhibitors indicate that translation, but not transcription, is
required for activation of the TonEBPs. Phosphorylation is required
for the stimulation of transcription but not for activation of DNA
binding by the TonEBPs. In vivo methylation by dimethyl sulfate
reveals that the TonE site of the BGT1 gene is protected with a time
course like that of activity of the TonEBPs and activation of
transcription. UV cross-linking indicates that the TonEBPs share a
DNA binding subunit of 200 kD.
Received 9 September 1997; accepted in final form 8 January 1998.
APS Manuscript Number F289-7.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 28 January 1998