Physical evidence for distinct mechanisms of translational control by upstream open reading frames
AUTOR(ES)
Gaba, Anthony
FONTE
Oxford University Press
RESUMO
The Saccharomyces cerevisiae GCN4 mRNA 5′-leader contains four upstream open reading frames (uORFs) and the CPA1 leader contains a single uORF. To determine how these uORFs control translation, we examined mRNAs containing these leaders in cell-free translation extracts to determine where ribosomes were loaded first and where they were loaded during steady-state translation. Ribosomes predominantly loaded first at GCN4 uORF1. Following its translation, but not the translation of uORF4, they efficiently reinitiated protein synthesis at Gcn4p. Adding purified eIF2 increased reinitiation at uORFs 3 or 4 and reduced reinitiation at Gcn4p. This indicates that eIF2 affects the site of reinitiation following translation of GCN4 uORF1 in vitro. In contrast, for mRNA containing the CPA1 uORF, ribosomes reached the downstream start codon by scanning past the uORF. Addition of arginine caused ribosomes that had synthesized the uORF polypeptide to stall at its termination codon, reducing loading at the downstream start codon, apparently by blocking scanning ribosomes, and not by affecting reinitiation. The GCN4 and CPA1 uORFs thus control translation in fundamentally different ways.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=125715Documentos Relacionados
- Translational Control of Protein Kinase Cη by Two Upstream Open Reading Frames ▿
- Suppression of ribosomal reinitiation at upstream open reading frames in amino acid-starved cells forms the basis for GCN4 translational control.
- Upstream Open Reading Frames as Regulators of mRNA Translation
- Role of an upstream open reading frame in mediating arginine-specific translational control in Neurospora crassa.
- One protein from two open reading frames: mechanism of a 50 nt translational bypass