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RNA in polysomes is an inhibitor of manganese superoxide dismutase RNA-binding protein activity
1Department of Physiology, Georgetown University School of Medicine, Washington, District of Columbia 20007, USA.
Abstract:
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.
Insights
A developmental difference in manganese superoxide dismutase mRNA binding protein (Mn-SOD-BP) activity is due to an RNA inhibitor present in adult rat lung tissue. This inhibitor in the P130 fraction reduces Mn-SOD-BP activity, impacting gene expression.
Area of Science:
- Molecular Biology
- Developmental Biology
- Biochemistry
Background:
- A redox-sensitive protein binds the 3'-UTR of manganese superoxide dismutase (Mn-SOD) mRNA.
- Mn-SOD RNA-binding protein (Mn-SOD-BP) activity is higher in neonatal rat lung supernatant (S12) compared to adults.
Purpose of the Study:
- To investigate the mechanism behind the developmental difference in Mn-SOD-BP activity.
- To identify factors contributing to altered Mn-SOD mRNA binding in neonatal versus adult rat lungs.
Main Methods:
- Fractionation of rat lung tissue into subcellular components (S12, S130, P130).
- Assay of Mn-SOD-BP activity in different fractions.
- Testing the inhibitory effect of the P130 fraction on Mn-SOD-BP binding.
Main Results:
- The developmental difference in Mn-SOD-BP activity was not observed in the S130 fraction.
- The P130 fraction contained an inhibitor of Mn-SOD-BP activity.
- Adult P130 exhibited stronger inhibition of RNA binding than neonatal P130, indicating an age-dependent inhibitor.
Conclusions:
- The developmental variation in Mn-SOD-BP activity is partly mediated by an inhibitor found in the P130 fraction.
- This inhibitor is an RNA molecule, suggesting a role in the posttranscriptional regulation of Mn-SOD gene expression.