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Inhibition of protein synthesis stabilizes histone mRNA
Abstract:
The inhibition of protein synthesis in exponentially growing S49 cells leads to a specific fivefold increase in histone mRNA in 30 min. The rate of transcription of histone mRNA, measured in intact or digitonin-permeabilized cells, is increased slightly, if at all, by cycloheximide inhibition of protein synthesis. Both approach-to-equilibrium labeling and pulse-chase experiments show that cycloheximide prolongs histone mRNA half-life from approximately 30 min to greater than 2 h. Histone mRNA made before the addition of cycloheximide becomes stable after the inhibition of protein synthesis, whereas removal of the inhibitor is followed by rapid degradation of histone mRNA. This suggests that the increased stability of histone mRNA during inhibition of protein synthesis results not from alteration of the structure of the mRNA, but from the loss of an activity in the cell which regulates histone mRNA turnover.
Insights
Inhibiting protein synthesis rapidly increases histone mRNA levels by stabilizing existing mRNA. This suggests a cellular factor, not mRNA structure, controls histone mRNA turnover.
Area of Science:
- Molecular Biology
- Gene Regulation
- Cellular Processes
Background:
- Histone mRNA is crucial for DNA replication and cell proliferation.
- The regulation of histone mRNA stability is not fully understood.
- Protein synthesis inhibition is known to affect gene expression.
Purpose of the Study:
- To investigate the effect of protein synthesis inhibition on histone mRNA levels and stability.
- To determine the mechanism underlying the changes in histone mRNA abundance.
Main Methods:
- Utilizing S49 cells and cycloheximide to inhibit protein synthesis.
- Measuring histone mRNA levels via transcription rate assays.
- Assessing mRNA half-life using approach-to-equilibrium labeling and pulse-chase experiments.
Main Results:
- Protein synthesis inhibition caused a fivefold increase in histone mRNA within 30 minutes.
- Transcription rates showed minimal change upon cycloheximide treatment.
- Histone mRNA half-life extended from ~30 minutes to over 2 hours with inhibited protein synthesis.
Conclusions:
- Cycloheximide stabilizes histone mRNA, increasing its abundance without significantly altering transcription.
- The stability of histone mRNA is regulated by a labile cellular activity, not inherent mRNA structure.
- This labile activity is lost upon protein synthesis inhibition, leading to mRNA stabilization.