Post-termination ribosome interactions with the 5'UTR modulate yeast mRNA stability

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Post-transcriptional control mechanisms regulate gene expression after transcription.
• The 5' untranslated region (5'UTR) of mRNA plays a crucial role in translation and mRNA stability.
• Upstream open reading frames (uORFs) within 5'UTRs can influence gene expression.

Purpose of the Study:

• To investigate a novel mechanism of post-transcriptional control mediated by uORFs in the Saccharomyces cerevisiae Yap2 gene.
• To elucidate the role of the 5'UTR of the Yap2 gene in regulating mRNA turnover.
• To understand how uORFs affect gene expression at the level of mRNA decay.

Main Methods:

• Analysis of the Saccharomyces cerevisiae Yap2 gene and its 5'UTR.
• Identification and characterization of two upstream open reading frames (uORF1 and uORF2) within the Yap2 5'UTR.
• Investigation of mRNA turnover rates and the role of ribosome release and mRNA secondary structure in decay.
• Examination of the influence of translational factors like eIF2.

Main Results:

• The Yap2 5'UTR contains two uORFs (uORF1 and uORF2) that attenuate gene expression via termination-dependent mRNA decay.
• Release of post-termination ribosomes from the Yap2 5'UTR triggers accelerated mRNA decay, largely independent of UPF1.
• A G/C-rich stop codon context enables uORFs to act as transferable 5'UTR-destabilizing elements.
• Stable secondary structure 3' to the uORF stop codon potentiates destabilization, influenced by eIF2 and ribosome reinitiation kinetics.

Conclusions:

• YAP2-type uORFs function as cis-acting elements that destabilize mRNA through a termination-dependent decay pathway.
• Ribosome release from uORFs, influenced by stop codon context and mRNA structure, is a key driver of accelerated decay.
• This mechanism provides a general model for uORF-mediated mRNA destabilization, applicable to other genes like GCN4.