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Changes in distribution of actin mRNA in different polysome fractions following stimulation of MPC-11 cells
A J Johannessen1, I F Pyrme, A Vedeler
1Department of Biochemistry and Molecular Biology, University of Bergen, Norway.
Abstract:
Individual mRNA species have been shown to differ both with respect to localization in the cell, and in their distribution upon stimulation of cells with different signals. In this study we have examined the distribution of actin mRNA in the free, cytoskeletal-bound, and membrane-bound RNA fractions, both in starved cells, and in response to stimulation by feeding. These results were then compared with mRNAs for glyceraldehyde 3-phosphate dehydrogenase (GAPDH), and histone H4. The results we obtained showed that actin mRNA was located in the free RNA fraction in starved cells, while upon stimulation it was located both in the free, and in the cytoskeletal fraction; no redistribution of GAPDH mRNA occurred between the three RNA fractions, while H4 mRNA showed a different localization upon stimulation. Incubation with the drugs actinomycin-D and cycloheximide showed that an altered localization of actin mRNA from free in starved cells to free and cytoskeletal mRNA fractions following stimulation, was dependent on RNA synthesis, and not on protein synthesis.
Insights
Actin mRNA shifts from free to cytoskeletal fractions upon cell stimulation, a process dependent on RNA synthesis, not protein synthesis. This dynamic localization differs from GAPDH and H4 mRNA responses.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Messenger RNA (mRNA) localization within cells is crucial for protein synthesis and cellular function.
- Different mRNA species exhibit distinct distributions and dynamic changes in response to cellular signals.
Purpose of the Study:
- To investigate the cellular distribution of actin mRNA in response to feeding stimulation.
- To compare the localization patterns of actin mRNA with glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and histone H4 mRNAs.
- To determine the dependence of actin mRNA redistribution on RNA and protein synthesis.
Main Methods:
- Fractionation of cellular RNA into free, cytoskeletal-bound, and membrane-bound pools.
- Analysis of mRNA distribution in starved and stimulated cells.
- Treatment with actinomycin-D (inhibits RNA synthesis) and cycloheximide (inhibits protein synthesis).
Main Results:
- In starved cells, actin mRNA was primarily in the free RNA fraction.
- Upon stimulation, actin mRNA redistributed to both free and cytoskeletal fractions.
- GAPDH mRNA showed no redistribution, while H4 mRNA exhibited altered localization post-stimulation.
- Actin mRNA redistribution was dependent on RNA synthesis but independent of protein synthesis.
Conclusions:
- Actin mRNA undergoes dynamic, stimulus-dependent localization changes within the cell.
- The observed redistribution of actin mRNA is regulated by RNA synthesis, highlighting a post-transcriptional regulatory mechanism.
- Differential mRNA localization contributes to cellular responses to external signals.