mRNA quality control is bypassed for immediate export of stress-responsive transcripts

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• Cells require specific conditions for growth and survival.
• Stressful conditions necessitate rapid production of protective proteins (chaperones).
• Cells prioritize heat-shock protein synthesis by altering mRNA processing and export.

Purpose of the Study:

• To elucidate the mechanism of selective mRNA export during cellular stress.
• To understand how cells differentiate between regular and heat-shock mRNAs for export.
• To identify the roles of RNA adaptor proteins and Mex67-Mtr2 in stress-induced mRNA export.

Main Methods:

• Investigated mRNA export pathways in Saccharomyces cerevisiae.
• Utilized genetic and molecular biology techniques to study protein-RNA interactions.
• Analyzed the role of heat-shock transcription factor Hsf1 in stress-responsive gene expression.

Main Results:

• Cellular stress causes dissociation of adaptor proteins from regular mRNAs, inhibiting their export.
• Heat-shock mRNAs are exported rapidly, directly associating with the Mex67-Mtr2 complex without adaptors.
• Heat-shock mRNA export bypasses the stringent quality control mechanisms applied to regular mRNAs.
• The transcription factor Hsf1 facilitates direct co-transcriptional loading of Mex67 onto heat-shock mRNAs.

Conclusions:

• Cells employ a dual strategy for mRNA export: quality-controlled export for regular mRNAs and rapid, uncontrolled export for stress-responsive mRNAs.
• This selective export mechanism allows for immediate synthesis of protective proteins, crucial for cell survival under extreme conditions.
• The fate of an mRNA (quality control or direct export) is determined by its promoter, highlighting a regulatory switch for stress response.