Promoter elements which mediate the ph-response of
phosphoenolpyruvate carboxykinase mrna in llc-pk1-f+ cells.
Holcomb, Thomas, Wenlin Liu, Richard Snyder, Richard Shapiro, and
Norman P. Curthoys.
Department of Biochemistry and Molecular Biology, Colorado State
University, Fort Collins, CO 80523, USA
APStracts 3:0053F, 1996.
The onset of metabolic acidosis causes an increased transcription of
the renal phosphoenolpyruvate carboxykinase (PCK) gene. When
transgenic mice carrying a bovine growth hormone (bGH) gene driven by
the -460 to +73 segment of the PCK promoter were made chronically
acidotic, the bGH mRNA was increased 2-fold after 4 d. Confluent and
well-differentiated cultures of LLC-PK1-F+ cells exhibit a 2.5-fold
increase in PCK mRNA when transferred to acidic media (pH 6.9, 10 mM
HCO3-) for 16 h. Confluent cultures transfected with PCK-490CAT
exhibit an increase (3.5-fold) in chloramphenicol acetyltransferase
(CAT) activity when shifted to acidic medium for 48 h. Mutation or
deletion of the P2 element causes a 4- to 5-fold decrease in basal
CAT activity but does not affect the pH-response. In contrast,
mutations of the P3(II) element or CRE-1 have little effect on basal
activity, but cause a 50% decrease in the pH-response. Other
deletions or mutations have little effect on either activity. Thus,
changes in the activity or levels of the protein(s) in the renal
proximal tubule which bind to the P3(II) and CRE-1 elements may
mediate increased transcription of the PCK gene during metabolic
acidosis.
Received 11 October 1995; accepted in final form 8 March 1996.
APS Manuscript Number F340-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 27 March 96