AJP - Lung Cellular and Molecular Physiology, Vol 272, Issue 4 714-L719, Copyright © 1997 by American Physiological Society
RNA in polysomes is an inhibitor of manganese superoxide dismutase RNA-binding protein activity
D. J. Chung and L. B. Clerch
Department of Physiology, Georgetown University School of Medicine, Washington, District of Columbia 20007, USA.
A redox-sensitive protein in rat lung binds to the 3'-untranslated region
(3'-UTR) of manganese superoxide dismutase (Mn-SOD) mRNA; the activity of
this Mn-SOD RNA-binding protein (Mn-SOD-BP) is greater in 12,000-g
supernatant fractions (S12) from neonates than in S12 from adults (H.
Fazzone, A. Wangner, and L. B. Clerch. J. Clin. Invest. 92: 1278-1281,
1993). To determine the mechanism underlying this developmental difference,
lung subcellular fractions were tested for their effect on Mn-SOD-BP
activity. Protein in the 130,000-g supernatant (S130) of lung extracts
bound the 3'-UTR. However, the developmental difference in binding was not
present in S130. The 130,000-g pellet (P130) did not bind the 3'-UTR;
rather, it contained an inhibitor of Mn-SOD-BP activity. Addition of P130
to S130 decreased RNA binding in a dose-dependent manner. Furthermore,
adult P130 was a more potent inhibitor of RNA-binding activity than
neonatal P130. These data indicate that the developmental difference in
Mn-SOD-BP activity is due, in part, to an inhibitor in P130. Biochemical
characterization revealed that the inhibitor is an RNA that may participate
in the posttranscriptional control of Mn-SOD gene expression.
