title: Chrysovirus structure: repeated helical core as evidence of gene duplication.
abstract: Chrysoviruses are double-stranded RNA viruses with a multipartite genome. Structure of two fungal chrysoviruses, Penicillium chrysogenum virus and Cryphonectria nitschkei chrysovirus 1, has been determined by three-dimensional cryo-electron microscopy analysis and in hydrodynamic studies. The capsids of both viruses are based on a T=1 lattice containing 60 subunits, remain structurally undisturbed throughout the viral cycle, and participate in genome metabolism. The capsid protein is formed by a repeated α-helical core, indicative of gene duplication. Whereas the chrysovirus capsid protein has two motifs with the same fold, most dsRNA virus capsid subunits consist of dimers of a single protein with similar folds. The arrangement of the chrysovirus α-helical core is conserved in the totivirus L-A capsid protein, suggesting a shared basic fold. The encapsidated genome is organized in concentric shells; whereas inner dsRNA shells are diffuse, the outermost layer is organized into a dodecahedral cage beneath the protein capsid. This genome ordering could constitute a framework for dsRNA transcription in the capsid interior and/or have a structural role for capsid stability.
authors.affiliation: Department of Structure of Macromolecules, Centro Nacional Biotecnología/CSIC, Campus de Cantoblanco, Madrid, Spain. jrcaston@cnb.csic.es
authors.forename: José R
authors.initials: JR
authors.lastname: Castón
authors.forename: Daniel
authors.initials: D
authors.lastname: Luque
authors.forename: Josué
authors.initials: J
authors.lastname: Gómez-Blanco
authors.forename: Said A
authors.initials: SA
authors.lastname: Ghabrial
mesh_terms: D001203:Ascomycota / Q000821:virology*; D002213:Capsid / Q000648:ultrastructure; D036022:Capsid Proteins / Q000737:chemistry / Q000235:genetics*; D020285:Cryoelectron Microscopy; D020440:Gene Duplication; D021621:Imaging, Three-Dimensional; D011487:Protein Conformation; D017510:Protein Folding; D012328:RNA Viruses / Q000235:genetics* / Q000302:isolation & purification / Q000648:ultrastructure*
chemical_list: D036022:Capsid Proteins