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Functional recognition of fragmented operator sites by R17/MS2 coat protein, a translational repressor
D E Fouts1, H L True, D W Celander
1Department of Microbiology and College of Medicine, University of Illinois at Urbana-Champaign, B103 Chemical and Life Sciences Laboratory, 601 South Goodwin Avenue, Urbana, IL 61801, USA.
Nucleic Acids Research
|February 12, 1998
Summary
The R17/MS2 coat protein represses gene translation by binding RNA hairpins. Its regulatory function extends beyond natural sites, highlighting protein control over RNA folding for bacterial gene regulation.
Area of Science:
- Molecular Biology
- Bacteriology
- Genetics
Background:
- The R17/MS2 coat protein acts as a translational repressor.
- It binds to a specific RNA hairpin structure that includes the Shine-Dalgarno sequence and initiation codon.
- This interaction regulates the expression of the replicase gene.
Purpose of the Study:
- To investigate the structural requirements of the RNA operator site for R17/MS2 coat protein-mediated translational repression in vivo.
- To determine the extent of the coat protein's regulatory influence beyond the natural operator site.
Main Methods:
- Construction of bacteriophage P22 derivatives carrying modified R17/MS2 RNA operator sites.
- In vivo analysis of lysogen formation to assess translational repression efficiency.
- Engineering fragmented operator sites to alter the positioning of the Shine-Dalgarno sequence and initiation codon relative to the RNA hairpin.
Main Results:
- The wild-type R17/MS2 coat protein efficiently repressed translation even when the Shine-Dalgarno sequence was located outside the hairpin.
- Repression was not observed when the hairpin was positioned 9 nucleotides away from the Shine-Dalgarno sequence, defining a critical region for interaction.
- Translational repression is achieved by preventing ribosome access through stable RNA secondary structure formation, not solely by capsid assembly.
Conclusions:
- The R17/MS2 coat protein's translational repression is dependent on the spatial arrangement of RNA structural elements.
- The protein's regulatory activity can extend beyond the canonical operator site by inducing specific RNA folding.
- Bacterial translational regulation involves proteins modulating RNA folding states for mRNA transcripts.