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Translation of poly(A)-binding protein mRNA is regulated by growth conditions
1Department of Molecular Biology and Genetics, College of Biological Science, University of Guelph, Ont., Canada.
Abstract:
Translational efficiency of a minor group of mRNAs is regulated by serum levels in 3T6 fibroblasts. Included within this group is the poly(A)-binding protein (PABP) mRNA. We analyzed the distribution of PABP mRNA in polysome profiles and found a large percentage of this mRNA to be translationally repressed in both actively growing (approximately 60%) and resting cells (approximately 70%). Elevated serum levels induced a distinct bimodal distribution of this mRNA between actively translated and repressed fractions. Similarly, treatment of cells with low doses of cycloheximide also generated a partial shift of repressed PABP mRNA into the actively translated fraction. In an attempt to characterize the factors which regulate PABP mRNA translation we have identified the proteins which bind to this mRNA in vitro. Sequences within the 5' untranslated region were found to be sufficient for binding of all proteins to this mRNA. We suggest that this region and the proteins associated with it may be essential for translation control of PABP mRNA.
Insights
Serum levels regulate the translation of poly(A)-binding protein (PABP) mRNA in fibroblasts. This regulation involves shifts in PABP mRNA distribution between repressed and actively translated states, mediated by protein binding to its 5' untranslated region.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Translational control is crucial for gene expression regulation.
- Specific messenger RNAs (mRNAs) are sensitive to extracellular signals like serum levels.
- Poly(A)-binding protein (PABP) mRNA is implicated in translational regulation.
Purpose of the Study:
- To investigate the regulation of PABP mRNA translation by serum levels in 3T6 fibroblasts.
- To characterize the proteins that bind to PABP mRNA and their role in translational control.
Main Methods:
- Analysis of PABP mRNA distribution in polysome profiles.
- Treatment of cells with elevated serum levels and cycloheximide.
- In vitro identification of proteins binding to PABP mRNA.
Main Results:
- A significant portion of PABP mRNA was translationally repressed in both growing and resting cells.
- Elevated serum levels and cycloheximide treatment shifted PABP mRNA towards active translation.
- Proteins binding to the 5' untranslated region of PABP mRNA were identified.
Conclusions:
- PABP mRNA translation is regulated by serum levels in fibroblasts.
- The 5' untranslated region of PABP mRNA and associated proteins are critical for its translational control.