| Structural highlights
Function
[CAPSD_BPMS2] Self-assembles to form the T=3 icosahedral virus shell that protects the viral nucleic acid. Acts as a translational repressor by binding with high specificity to a single stem-loop structure in the genomic RNA that contains the initiation codon of the gene for the viral replicase. Involved in virus assembly through the interaction between a capsid protein dimer and the multiple packaging signals present in the RNA genome.[1] [2] [3] [4] [5] [6] [MAT_BPMS2] The maturation protein is required for the typical attachment of the phage to the side of the bacterial pili (PubMed:23810697). MP binds to sequences located toward each end of the genome, hence circularizing it (PubMed:26608810). The RNA genome-MP complex is released from the capsid upon host receptor binding (PubMed:23810697). MP enters the cell along with the viral RNA (PubMed:4551992).[7] [8] [9]
Publication Abstract from PubMed
Packaging of the genome into a protein capsid and its subsequent delivery into a host cell are two fundamental processes in the life cycle of a virus. Unlike double-stranded DNA viruses, which pump their genome into a preformed capsid, single-stranded RNA (ssRNA) viruses, such as bacteriophage MS2, co-assemble their capsid with the genome; however, the structural basis of this co-assembly is poorly understood. MS2 infects Escherichia coli via the host 'sex pilus' (F-pilus); it was the first fully sequenced organism and is a model system for studies of translational gene regulation, RNA-protein interactions, and RNA virus assembly. Its positive-sense ssRNA genome of 3,569 bases is enclosed in a capsid with one maturation protein monomer and 89 coat protein dimers arranged in a T = 3 icosahedral lattice. The maturation protein is responsible for attaching the virus to an F-pilus and delivering the viral genome into the host during infection, but how the genome is organized and delivered is not known. Here we describe the MS2 structure at 3.6 A resolution, determined by electron-counting cryo-electron microscopy (cryoEM) and asymmetric reconstruction. We traced approximately 80% of the backbone of the viral genome, built atomic models for 16 RNA stem-loops, and identified three conserved motifs of RNA-coat protein interactions among 15 of these stem-loops with diverse sequences. The stem-loop at the 3' end of the genome interacts extensively with the maturation protein, which, with just a six-helix bundle and a six-stranded beta-sheet, forms a genome-delivery apparatus and joins 89 coat protein dimers to form a capsid. This atomic description of genome-capsid interactions in a spherical ssRNA virus provides insight into genome delivery via the host sex pilus and mechanisms underlying ssRNA-capsid co-assembly, and inspires speculation about the links between nucleoprotein complexes and the origins of viruses.
In situ structures of the genome and genome-delivery apparatus in a single-stranded RNA virus.,Dai X, Li Z, Lai M, Shu S, Du Y, Zhou ZH, Sun R Nature. 2017 Jan 5;541(7635):112-116. doi: 10.1038/nature20589. Epub 2016 Dec 19. PMID:27992877[10]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Horn WT, Tars K, Grahn E, Helgstrand C, Baron AJ, Lago H, Adams CJ, Peabody DS, Phillips SE, Stonehouse NJ, Liljas L, Stockley PG. Structural basis of RNA binding discrimination between bacteriophages Qbeta and MS2. Structure. 2006 Mar;14(3):487-95. PMID:16531233 doi:http://dx.doi.org/10.1016/j.str.2005.12.006
- ↑ Plevka P, Tars K, Liljas L. Crystal packing of a bacteriophage MS2 coat protein mutant corresponds to octahedral particles. Protein Sci. 2008 Oct;17(10):1731-9. Epub 2008 Jul 28. PMID:18662904 doi:10.1110/ps.036905.108
- ↑ Rolfsson O, Middleton S, Manfield IW, White SJ, Fan B, Vaughan R, Ranson NA, Dykeman E, Twarock R, Ford J, Kao CC, Stockley PG. Direct Evidence for Packaging Signal-Mediated Assembly of Bacteriophage MS2. J Mol Biol. 2016 Jan 29;428(2 Pt B):431-48. doi: 10.1016/j.jmb.2015.11.014. Epub , 2015 Dec 1. PMID:26608810 doi:http://dx.doi.org/10.1016/j.jmb.2015.11.014
- ↑ Golmohammadi R, Valegard K, Fridborg K, Liljas L. The refined structure of bacteriophage MS2 at 2.8 A resolution. J Mol Biol. 1993 Dec 5;234(3):620-39. PMID:8254664 doi:http://dx.doi.org/10.1006/jmbi.1993.1616
- ↑ Valegard K, Murray JB, Stonehouse NJ, van den Worm S, Stockley PG, Liljas L. The three-dimensional structures of two complexes between recombinant MS2 capsids and RNA operator fragments reveal sequence-specific protein-RNA interactions. J Mol Biol. 1997 Aug 1;270(5):724-38. PMID:9245600 doi:http://dx.doi.org/10.1006/jmbi.1997.1144
- ↑ van den Worm SH, Stonehouse NJ, Valegard K, Murray JB, Walton C, Fridborg K, Stockley PG, Liljas L. Crystal structures of MS2 coat protein mutants in complex with wild-type RNA operator fragments. Nucleic Acids Res. 1998 Mar 1;26(5):1345-51. PMID:9469847
- ↑ Dent KC, Thompson R, Barker AM, Hiscox JA, Barr JN, Stockley PG, Ranson NA. The Asymmetric Structure of an Icosahedral Virus Bound to Its Receptor Suggests a Mechanism for Genome Release. Structure. 2013 Jun 25. pii: S0969-2126(13)00194-9. doi:, 10.1016/j.str.2013.05.012. PMID:23810697 doi:10.1016/j.str.2013.05.012
- ↑ Rolfsson O, Middleton S, Manfield IW, White SJ, Fan B, Vaughan R, Ranson NA, Dykeman E, Twarock R, Ford J, Kao CC, Stockley PG. Direct Evidence for Packaging Signal-Mediated Assembly of Bacteriophage MS2. J Mol Biol. 2016 Jan 29;428(2 Pt B):431-48. doi: 10.1016/j.jmb.2015.11.014. Epub , 2015 Dec 1. PMID:26608810 doi:http://dx.doi.org/10.1016/j.jmb.2015.11.014
- ↑ Krahn PM, O'Callaghan RJ, Paranchych W. Stages in phage R17 infection. VI. Injection of A protein and RNA into the host cell. Virology. 1972 Mar;47(3):628-37. PMID:4551992
- ↑ Dai X, Li Z, Lai M, Shu S, Du Y, Zhou ZH, Sun R. In situ structures of the genome and genome-delivery apparatus in a single-stranded RNA virus. Nature. 2017 Jan 5;541(7635):112-116. doi: 10.1038/nature20589. Epub 2016 Dec 19. PMID:27992877 doi:http://dx.doi.org/10.1038/nature20589
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