Characterization of the rat nhe3 promoter.
Cano, Adriana.
Department of Internal Medicine, The University of Texas
Southwestern Medical Center, Dallas, TX 75235
APStracts 3:0096F, 1996.
NHE3, a transmembrane protein involved in transcellular ion transport,
is expressed in the apical membrane of renal and gastrointestinal
epithelia. Chronic regulation by multiple stimuli including
glucocorticoid-induced transcriptional regulation has been
demonstrated. To study the tissue-specific expression and
transcriptional regulation of NHE3 the 5' flanking region of the rat
NHE3 gene was cloned. Two genomic libraries were screened with the 5'
end of the NHE3 cDNA. The 5' flanking region and first exon were
isolated. Primer extension mapped a single transcription start site
in stomach, colon and kidney. The NHE3 promoter near the
transcription initiation site is characterized by the absence of TATA
and CAAT sequences. Two Sp1 sites, one Egr-1 site and an initiator
with the sequence GGGATTAAA mark the area of transcription
initiation. Upstream sequences include multiple DNA sequence elements
recognized by the glucocorticoid and thyroid receptors, Sp1, AP-2 and
several other transcription factors. Transcriptional regulation by
glucocorticoids and chronic acidosis was demonstrated. Promoter
activity was present in OKP cells, a renal proximal tubule cell line,
but not in fibroblasts. This suggests that the NHE3 promoter contains
elements conferring epithelial cell specific expression.
Received 26 December 1995; accepted in final form 9 May 1996.
APS Manuscript Number F428-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 June 96