The 3'-nontranslated region of rat renal glutaminase mrna contains
a ph-responsive stability element.
Hansen, William R., Nancy Barsic-Tress, Lynn Taylor, and Norman P.
Curthoys.
Department of Biochemistry and Molecular Biology, Colorado State
University, Fort Collins, CO 80523-1870
APStracts 3:0034F, 1996.
Rat kidney expresses two forms of glutaminase (GA) mRNA which probably
result from the use of alternative polyadenylation signals. The two
mRNAs are increased coordinately in response to metabolic acidosis
via a mechanism that apparently does not involve transcriptional or
translational regulation. A 956-bp fragment which contains the 3'
-nontranslated sequence of the smaller GA cDNA was cloned into an
expression vector (p[beta]G) which encodes a chimeric [beta]-globin
-growth hormone mRNA. Both the parent and the derived construct
(p[beta]G-GA) were transfected into LLC-PK1-F+ cells . Stable
transfectants express 6-fold lower levels of [beta]G-GA mRNA than
that of the parent [beta]G mRNA. However, only the [beta]G-GA mRNA is
increased 2.5-fold by growth in acidic medium (pH 6.9, 10 mM HCO3-).
The apparent half-life of the [beta]G mRNA (>24 h) is unaffected
by the pH of the growth media. In contrast, the apparent half-life of
the [beta]G-GA mRNA is increased from 4.5 h to approximately 24 h
when cells are transferred to acidic medium for 8 h. The observed pH
-response is not reproduced when the [beta]G-GA construct is stably
transfected into cos 7 cells or when a [beta]-globin
-phosphoenolpyruvate carboxykinase chimeric gene is expressed in LLC
-PK1-F+ cells. Thus, the 3'-nontranslated region of the GA mRNA
contains a pH-responsive stability element.
Received 24 August 1995; accepted in final form 8 February 1996.
APS Manuscript Number F284-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 13 March 96