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Translational control by an upstream open reading frame in the HER-2/neu transcript.
S J Child1, M K Miller, A P Geballe
1Divisions of Human Biology and Clinical Research, C2-023, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109, USA.
The Journal of Biological Chemistry
|August 14, 1999
Summary
A short sequence in HER-2 mRNA, an upstream open reading frame (uORF), inhibits protein production. This HER-2 uORF limits ribosome access to translation start sites, controlling oncoprotein synthesis.
Area of Science:
- Molecular Biology
- Cancer Research
- Gene Regulation
Background:
- HER-2 (neu, erbB-2) receptor overexpression drives cellular transformation and is linked to various human cancers.
- HER-2 expression is tightly regulated by multiple mechanisms, including gene amplification and post-transcriptional/translational controls.
Purpose of the Study:
- To elucidate the inhibitory mechanism of a short upstream open reading frame (uORF) within HER-2 mRNA.
- To understand how this HER-2 uORF regulates downstream translation and oncoprotein synthesis.
Main Methods:
- Analysis of protein and mRNA abundance.
- Polysomal distribution analyses.
- Translation assays using HER-2 cistrons and heterologous reporter genes.
Main Results:
- The HER-2 uORF significantly represses translation of downstream genes, independent of its peptide sequence.
- Most ribosomes translating the uORF fail to reinitiate translation at the downstream start codon due to short intercistronic spacing.
- A small fraction of ribosomes access the HER-2 initiation codon via leaky scanning or reinitiation.
Conclusions:
- The HER-2 uORF acts as a translational repressor by limiting ribosomal access to initiation sites.
- This mechanism provides a crucial control point for the synthesis of the HER-2 oncoprotein.