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Interference with bacteriophage phi 6 genomic RNA packaging by hairpin structures
1Department of Microbiology, Public Health Research Institute, New York, New York 10016, USA.
Journal of Virology
|September 1, 1995
Summary
Bacteriophage phi 6 packaging involves 5' end entry, excluding hairpin-containing 3' ends. This mechanism prevents recombination and suggests multiple procapsid entry pores for genomic segment packaging.
Area of Science:
- Molecular Biology
- Virology
- Genetics
Background:
- Bacteriophage phi 6 possesses a three-segment double-stranded RNA genome.
- The genome is enclosed within a procapsid made of four proteins.
- Procapsids can package plus-strand RNA transcripts in vitro, followed by minus-strand synthesis.
Purpose of the Study:
- To investigate the mechanism of genomic segment packaging in bacteriophage phi 6.
- To determine the role of hairpin structures in 3' ends of RNA transcripts during packaging.
- To understand the dependency of segment M packaging on segment S.
Main Methods:
- In vitro packaging reactions using bacteriophage phi 6 procapsids and plus-strand RNA transcripts.
- Analysis of excluded sequences from packaged particles when hairpin structures are present.
- Investigating the effect of hairpin-containing S segment on M segment packaging.
Main Results:
- Sequences bounded by or 3' to hairpin structures are excluded from packaged particles.
- Packaging is inferred to initiate from the 5' end of the RNA transcripts.
- Hairpin-containing S segment facilitates packaging of M segment, suggesting multiple entry pores.
Conclusions:
- Hairpin structures at the 3' end of RNA transcripts inhibit packaging, supporting a 5'-end-first packaging model.
- The facilitation of recombination by hairpins is due to exclusion of the 3' end, not polymerase progression difficulty.
- The packaging dependency and facilitation between segments S and M imply the existence of multiple procapsid entry pores.