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A dual upstream open reading frame-based autoregulatory circuit controlling polyamine-responsive translation
Colin Hanfrey1, Katherine A Elliott, Marina Franceschetti
1Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, United Kingdom.
The Journal of Biological Chemistry
|September 24, 2005
Summary
A novel translational regulation mechanism for S-adenosylmethionine decarboxylase (AdoMetDC) involves two upstream open reading frames (uORFs) in plants. A small uORF peptide represses translation, while a tiny uORF regulates polyamine responses.
Area of Science:
- Molecular Biology
- Plant Science
- Gene Regulation
Background:
- Polyamines are essential for cell growth and proliferation.
- S-adenosylmethionine decarboxylase (AdoMetDC) is a key enzyme in polyamine biosynthesis.
- Translational control is a critical layer of gene expression regulation.
Purpose of the Study:
- To investigate the novel translational regulation of plant AdoMetDC.
- To identify the roles of upstream open reading frames (uORFs) in AdoMetDC mRNA.
- To explore the evolutionary conservation of this regulatory mechanism.
Main Methods:
- Analysis of plant AdoMetDC mRNA 5' leaders.
- In vitro expression studies.
- Functional assays in Saccharomyces cerevisiae.
Main Results:
- Plant AdoMetDC mRNA 5' leaders contain two conserved, overlapping uORFs: tiny and small.
- The small uORF peptide constitutively represses downstream AdoMetDC translation.
- The tiny uORF is essential for polyamine-responsive translation, potentially via ribosomal leaky scanning or frameshifting.
Conclusions:
- A novel sequence-dependent uORF-mediated translational repression mechanism is described for plant AdoMetDC.
- This regulatory system, involving tiny and small uORFs, is conserved across diverse plant species and functional in yeast.
- The findings suggest an ancient origin for uORF-based translational control in eukaryotes.