Internal/Structures Containing Transcriptase-Related Proteins in Top Component Particles of Mammalian Orthoreovirus

Dryden, Kelly A.; Farsetta, Diane L.; Wang, Guoji; Keegan, Jesse; Fields, Bernard N.; Baker, Timothy S.; Nibert, Max L.

doi:10.1006/viro.1998.9146

Cited by 82 publications

(87 citation statements)

References 58 publications

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“…4c,d). The broad interface between λ3 and λ1 suggests that λ3 is firmly anchored to the shell, consistent with the 'fixed-polymerase-movingtemplate' model of reovirus transcription 15,18,44,45 . Despite the inherent high noise level in the central parts of the cryo-EM map, 33 of the 48 α-helices in the λ3 X-ray crystal model were clearly identified and fitted by both SITUS and EMfit (Table 1).…”

Section: General Features Of the λ3 Fitsupporting

confidence: 72%

“…However, in none of these viruses have the positions and orientations of the RdRps been precisely determined. For all these viruses, a generally accepted, though largely unproven, model is that each of the 10-12 genome segments is dedicated to its own transcriptase complex within the particle 15,18,31,[35][36][37][38][39] .…”

Section: Nih-pa Author Manuscriptmentioning

confidence: 99%

“…The RdRp λ3 has been localized beneath each of the five-fold axes of the λ1 shell 11,15 , placing it in an approximate position to export mRNA into the λ2 turret for completion of capping and export. The RdRps in other members of the Reoviridae family, such as rotavirus [35][36] , bluetongue virus (orbivirus) [37][38] and cytoplasmic polyhedrosis virus (cypovirus) 39 , are also located beneath the five-fold axes of the inner shell.…”

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confidence: 99%

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Reovirus polymerase λ3 localized by cryo-electron microscopy of virions at a resolution of 7.6 Å

Zhang

Walker

Chipman

et al. 2003

Nat Struct Mol Biol

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Reovirus is an icosahedral, double-stranded (ds) RNA virus that uses viral polymerases packaged within the viral core to transcribe its ten distinct plus-strand RNAs. To localize these polymerases, the structure of the reovirion was refined to a resolution of 7.6 Å by cryo-electron microscopy (cryo-EM) and three-dimensional (3D) image reconstruction. X-ray crystal models of reovirus proteins, including polymerase λ3, were then fitted into the density map. Each copy of λ3 was found anchored to the inner surface of the icosahedral core shell, making major contacts with three molecules of shell protein λ1 and overlapping, but not centering on, a five-fold axis. The overlap explains why only one copy of λ3 is bound per vertex. λ3 is furthermore oriented with its transcript exit channel facing a small channel through the λ1 shell, suggesting how the nascent RNA is passed into the large external cavity of the pentameric capping enzyme complex formed by protein λ2.All viruses with either a single-stranded, minus-sense RNA genome (such as influenza and measles viruses) or a dsRNA genome (such as reoviruses and rotaviruses) must package virally encoded RNA-dependent RNA polymerase (RdRp) molecules within virions to transcribe the genome into single-stranded, plus-sense RNA for translation and replication during infection. The dsRNA viruses are distinct, however, in having icosahedral particles within which the RdRp molecules are regularly bound and the genome remains enclosed throughout transcription. dsRNA virus particles thus provide useful models in which to study structural aspects of RNA-dependent transcription.Reovirus, a member of the Reoviridae family of animal and plant viruses, has a genome comprising ten dsRNA segments, which are surrounded in virions by a multilayered, icosahedral protein capsid (diameter ~850 Å; mass ~110 MDa 1 ). The outer capsid layer is arranged with quasi T = 13(laevo) symmetry and includes 200 heterohexamers of the μ1 and σ3 proteins (μ1 3 σ3 3 ) (refs. 2,3) and 12 homotrimers of the σ1 protein [4][5][6][7] . These proteins are © 2003 Nature Publishing Group Correspondence should be addressed to T.S.B. (tsb@bilbo.bio.purdue.edu). COMPETING INTERESTS STATEMENTThe authors declare that they have no competing financial interests.Note: Supplementary information is available on the Nature Structural Biology website. NIH Public Access Author ManuscriptNat Struct Biol. Author manuscript; available in PMC 2014 September 03. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript released during cell entry after fulfilling their roles in stability (σ3), attachment (σ1) and membrane penetration (μ1) (refs. 8-10). The 15-MDa, 23.5-kilobase pair genome is encased by an inner capsid layer having T = 1 symmetry and composed of 60 dimers of the λ1 protein 11 . This inner layer remains surrounding the genome after cell entry and may protect it from eliciting dsRNA-dependent host responses 12,13 . Also in the subviral 'core' that enters the cytoplasm are two proteins external ...

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Section: General Features Of the λ3 Fitsupporting

confidence: 72%

Section: Nih-pa Author Manuscriptmentioning

confidence: 99%

mentioning

confidence: 99%

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Reovirus polymerase λ3 localized by cryo-electron microscopy of virions at a resolution of 7.6 Å

Zhang

Walker

Chipman

et al. 2003

Nat Struct Mol Biol

Self Cite

155

164

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“…Nascent mRNA is capped before being released from the intact capsid. The mechanism by which this characteristic endogenous transcription takes place inside intact dsRNA viruses has been studied extensively (3)(4)(5)(6)(7), and it is generally believed that the RNA polymerase complex is structurally anchored to the core during transcription (7)(8)(9). The dsRNA template must be flexible enough to move freely within the densely packed core so that it can slide through the RNAdependent RNA polymerase (RDRP) and the capping enzyme complex to ensure efficient transcription (10).…”

Section: Cpvmentioning

confidence: 99%

Structural Comparisons of Empty and Full Cytoplasmic Polyhedrosis Virus

Xia¹,

Jakana²,

Zhang³

et al. 2003

Journal of Biological Chemistry

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Viruses in the family Reoviridae are capable of transcription within the intact capsids. As the only singleshelled and thus the simplest member of the Reoviridae, cytoplasmic polyhedrosis virus (CPV) provides an attractive system for studying endogenous transcription. We report the structures of the full and empty CPV determined at 13-Å resolution by electron cryomicroscopy. The structure of the empty CPV reveals a density attributed to the transcription enzyme complex, which is attached to the internal surface of the capsid shell below each of the 12 turrets. The full capsid has an identical capsid shell but contains additional internal densities contributed by the genomic double-stranded (ds) RNA. The RNA densities proximal to the capsid shell are organized into layers with a dodecahedral appearance, suggesting a genome organization of dsRNA segments each having a cone shape spooling around a transcription enzyme complex. Our structures also suggest that the capsid shell serves as a scaffold for appropriate positioning of the RNA genome, whereas nascent mRNA release takes place through the constricted central channel of the turret. Based on these observations, a detailed moving template transcription mechanism is proposed that may provide insight into the well coordinated and highly efficient endogenous RNA transcription of dsRNA viruses.

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“…We present results regarding two virus structures, those of Sindbis and reo viruses [10]. The experimental data for the Sindbis virus consist of 7,917 views of 221 × 221 pixels each; the highest resolution obtained using existing algorithms is 11.2 Å.…”

Section: Resultsmentioning

confidence: 99%

Orientation refinement of virus structures with unknown symmetry

Marinescu

Zhang

et al. 2003

Proceedings International Parallel and Distributed Processing Symposium

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Structural biology, in particular the structure determination of viruses and other large macromolecular complexes leads to data-and compute-intensive problems that require resources well beyond those available on a single system. Thus, there is an imperative need to develop parallel algorithms and programs for clusters and computational grids. We present one of the most challenging computational problems posed by the three-dimensional structure determination of viruses, the orientation refinement.

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Internal/Structures Containing Transcriptase-Related Proteins in Top Component Particles of Mammalian Orthoreovirus

Cited by 82 publications

References 58 publications

Reovirus polymerase λ3 localized by cryo-electron microscopy of virions at a resolution of 7.6 Å

Reovirus polymerase λ3 localized by cryo-electron microscopy of virions at a resolution of 7.6 Å

Structural Comparisons of Empty and Full Cytoplasmic Polyhedrosis Virus

Orientation refinement of virus structures with unknown symmetry

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