Ribosome shunting in the cauliflower mosaic virus 35S RNA leader is a special case of reinitiation of translation functioning in plant and animal systems

The shunt model predicts that small ORFs (sORFs) within the cauliflower mosaic virus (CaMV) 35S RNA leader and downstream ORF VII are translated by different mechanisms, that is, scanning-reinitiation and shunting, respectively. Wheat germ extract (WGE) and rabbit reticulocyte lysate (RRL) in vitro...

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Bibliographic Details
Published in:Genes & development 2000-04, Vol.14 (7), p.817-829
Main Authors: Ryabova, L A, Hohn, T
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Animals
Base Sequence
Caulimovirus - genetics
Cell-Free System
Molecular Sequence Data
Nucleic Acid Conformation
Open Reading Frames
Peptide Chain Initiation, Translational
Plasmids
Protein Biosynthesis
Rabbits
Research Paper
Reticulocytes - metabolism
Ribosomes - genetics
Ribosomes - physiology
RNA, Spliced Leader - genetics
RNA, Viral - genetics
Seeds
Transcription, Genetic
Triticum
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Summary:The shunt model predicts that small ORFs (sORFs) within the cauliflower mosaic virus (CaMV) 35S RNA leader and downstream ORF VII are translated by different mechanisms, that is, scanning-reinitiation and shunting, respectively. Wheat germ extract (WGE) and rabbit reticulocyte lysate (RRL) in vitro translation systems were used to discriminate between these two processes and to study the mechanism of ribosomal shunt. In both systems, expression downstream of the leader occurred via ribosomal shunt under the control of a stable stem and a small ORF preceding it. Shunting ribosomes were also able to initiate quite efficiently at non-AUG start codons just downstream of the shunt landing site in WGE but not in RRL. The short sORF MAGDIS from the mammalian AdoMetDC RNA, which conditionally suppresses reinitiation at a downstream ORF, prevented shunting if placed at the position of sORF A, the 5'-proximal ORF of the CaMV leader. We have demonstrated directly that sORF A is translated and that proper termination of translation at the 5'-proximal ORF is absolutely required for both shunting and linear ribosome migration. These findings strongly indicate that shunting is a special case of reinitiation.
ISSN:0890-9369
1549-5477
DOI:10.1101/gad.14.7.817