Assembly of Proteins by Free RNA during the Early Phase of Proteostasis Stress

Area of Science:

• Cellular Biology
• Molecular Biology
• Proteostasis Research

Background:

• Messenger RNAs (mRNAs) are typically bound by proteins throughout their lifecycle.
• Stress conditions, such as heat shock, can induce polysome disassembly, leading to the transient appearance of free mRNAs in the cytosol.
• Understanding the proteins that interact with these free mRNAs is crucial for comprehending cellular responses to stress.

Purpose of the Study:

• To identify the cellular machinery that interacts with free RNA in mammalian cells undergoing heat shock.
• To characterize the structural and interaction properties of proteins associated with free mRNA during stress.
• To elucidate the mechanism of free RNA-protein complex formation and its regulation under proteostasis stress.

Main Methods:

• Quantitative mass spectrometry was employed to identify proteins associated with free RNA in heat-shocked mammalian cells.
• Structural analysis of identified RNA-binding proteins was performed.
• In vivo and in vitro reconstitution experiments were conducted to study protein-RNA interactions.

Main Results:

• Proteins interacting with free RNA exhibited increased intrinsic disorder and larger size, suggesting multivalent interactions.
• These interactors were identified as a distinct subset of RNA-binding proteins.
• The in vivo assembly of these protein complexes required RNA, and in vitro studies demonstrated a multimolecular basis for enhanced RNA binding upon heat shock.

Conclusions:

• Heat shock induces the formation of specific protein-RNA complexes involving intrinsically disordered proteins.
• These complexes play a role in managing free mRNA during proteostasis stress.
• The findings provide insights into the cellular mechanisms governing RNA processing under cellular stress conditions.