Protein Synthesis and Degradation
The cap-proximal RNA secondary structure inhibits preinitiation complex formation on HAC1 mRNATranslation of HAC1 mRNA in the budding yeast Saccharomyces cerevisiae is derepressed when RNase Ire1 removes its intron via nonconventional cytosolic splicing in response to accumulation of unfolded proteins inside the endoplasmic reticulum. The spliced HAC1 mRNA is translated into a transcription factor that changes the cellular gene expression patterns to increase the protein folding capacity of cells. Previously, we showed that a segment of the intronic sequence interacts with the 5′-UTR of the unspliced mRNA, resulting in repression of HAC1 translation at the initiation stage.
Evidence That Base-pairing Interaction between Intron and mRNA Leader Sequences Inhibits Initiation of HAC1 mRNA Translation in YeastBackground: Hac1 protein, encoded by a cytoplasmically spliced mRNA, activates the unfolded protein response to maintain cellular protein homeostasis and alleviate endoplasmic reticulum stress.Results: Under non-stress conditions, translation initiation on the HAC1 mRNA is repressed.Conclusion: Base-pairing interaction between the 5′ leader and intron represses translation initiation on the HAC1 mRNA.Significance: A unique mechanism of intron-mediated inhibition of ribosomal scanning.