Heat shock induces silent ribosomes and reorganizes mRNA turnover

Area of Science:

• Cell Biology
• Molecular Biology
• Stress Response

Background:

• Messenger RNAs (mRNAs) are translated by ribosomes into proteins.
• Ribosomal assemblies include monosomes (single ribosome) and polysomes (multiple ribosomes).
• The effect of heat stress on mRNA turnover and ribosome activity is not fully understood.

Purpose of the Study:

• To investigate the impact of heat stress on mRNA-ribosome association and ribosome status in yeast.
• To determine if silent monosomes are a general cellular adaptation to stress.

Main Methods:

• Yeast cells were subjected to heat shock.
• mRNA-ribosome association and the composition of ribosomal assemblies were analyzed.
• The presence of translational initiation factors and folding proteins in monosomes was assessed.

Main Results:

• Heat stress significantly increased the proportion of monosomes in yeast cells.
• Most heat-induced monosomes were silent, lacking associated mRNAs and key translation/folding proteins.
• Silent monosomes were also observed under other stress conditions, suggesting a general adaptive mechanism.
• Heat shock reduced overall mRNA-ribosome association but specifically promoted the translation of heat shock protein transcripts.
• mRNA half-lives were not extended for heat shock protein transcripts.

Conclusions:

• Heat stress induces a significant increase in silent monosomes as a cellular adaptation.
• This reorganization of mRNA turnover prioritizes the synthesis of heat shock proteins.
• Silent monosomes represent a conserved stress response mechanism across different stress types.