Negative regulation of the rat na,k-atpase [alpha]3 subunit gene
promoter by thyroid hormone.
He, Huaping, Shing Chin, Kai Zhuang, Ron Hartong, James Apriletti, and
Gregory Gick.
Department of Biochemistry, State University of New York Health
Science Center at Brooklyn, Brooklyn NY 11203, Division of
Endocrinology and Metabolism, Department of Medicine, University of
California, San Diego, CA 92103, and Metabolic Research Unit,
University of California, San Francisco CA 94143
APStracts 3:0178C, 1996.
Na,K-ATPase [alpha]3 subunit mRNA levels are both positively and
negatively controlled by thyroid hormone (T3) in primary cultures of
neonatal rat cardiac myocytes. In this study, transient transfection
analysis indicated that two regions of the rat [alpha]3 gene between
nucleotides -116 and -6 and -6 and +80 conferred T3-mediated
inhibition of reporter gene expression. Electrophoretic mobility
shift assays showed specific binding of T3 receptor monomers and T3
receptor/retinoid X receptor heterodimers at each [alpha]3 gene
negative T3-response region. The [alpha]3 gene region from -116 to -6
base pairs also mediates repression in response to retinoic acid (RA)
and binds RA receptor. In the absence of ligand, reporter gene
expression driven by the -116 to -6 base pair region is repressed
with cotransfection of T3 receptor while unaffected by overexpression
of RA receptor. These data demonstrate that the proximal promoter of
the rat Na,K-ATPase [alpha]3 gene contains sequence motifs which
mediate repression of [alpha]3 gene transcription in response to
either T3 or RA in neonatal rat cardiac myocytes.
Received 1 March 1996; accepted in final form 24 May 1996.
APS Manuscript Number C114-6.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 17 June 96