• Corpus ID: 194001401

Análisis estructural de los chrysovirus mediante criomicroscopía electrónica tridimensional: estuctura a resolución cuasi-atómica del virus de Penicillium chrysogenum

@inproceedings{Blanco2013AnlisisED,
  title={An{\'a}lisis estructural de los chrysovirus mediante criomicroscop{\'i}a electr{\'o}nica tridimensional: estuctura a resoluci{\'o}n cuasi-at{\'o}mica del virus de Penicillium chrysogenum},
  author={Josu{\'e} G{\'o}mez Blanco},
  year={2013}
}

• J. G. Blanco
• Published 2013
• Biology

Chrysoviruses are fungal double-stranded RNA viruses with a multipartite genome comprised of four monocistronic dsRNA segments. Each segment is separately encapsidated in a similar particle. Penicillium chrysogenum virus (PcV) is the type species of the family Chrysoviridae. The PcV capsid is an authentic T=1 lattice formed by 60 subunits, and the capsid protein appears to be a repeated a-helical domain, indicative of gene duplication. Whereas the PcV capsid protein has two motifs with a similar fold, most dsRNA virus capsid subunits consist of dimers of a single protein (a 120-subunit capsid). This ubiquitous stoichiometry provides an optimal framework for genome replication and organization. In addition, the capsid remains undisturbed throughout the viral cycle. We report the three-dimensional structures by single-particle cryo-electron microscopy (cryo- EM) analysis of two chrysoviruses, Cryphonectria nitschkei chrysovirus 1 (CnCV1) at subnanometer resolution and PcV at ~4 A resolution. Three-dimensional cryo-EM of CnCV1 at ~8 A resolution showed that the capsid protein (60 copies/particle) is formed by a repeated predominantly a-helical core. The arrangement of many of these putative a-helices is conserved in the PcV capsid protein. This unusual organization is thus a basic fold shared by chrysoviruses, and the duplicated structural signature for CnCV1 and PcV capsid proteins might derive from a gene duplication event. Our atomic model of the PcV virion from cryo-EM at ~4 A resolution is suitable for a nearly complete trace of the 982-amino-acid capsid protein. The full-atom model of the capsid showed the critical contacts among structural subunits that mediate capsid assembly, and specific RNAprotein interactions on the inner surface. Despite the lack of sequence similarity between the two halves, the capsid protein is an almost perfect structural duplication of a single domain in which most a-helices and b-chains matched very well. Superimposition of secondary structure elements showed, in addition to the N- and C-terminal arms, a single ?hot spot? into which structural and functional variations can be introduced by insertion of distinct segments. Overlaying L-A capsid protein (a totivirus with an undivided genome) on either of the PcV elements, while maintaining the same spatial arrangement in the shell, highlighted the same conserved PcV motif and hot spot for insertions, in addition to two new insertion zones. Structural comparison of PcV and other dsRNA viruses suggested that the PcV conserved core is partially preserved in Reoviridae. Our analysis detects three preferential sites at which the complexity of the preserved a-helical core might have increased and evolved to the highly varied structures observed today. The near-atomic structure of the PcV capsid protein derived from cryo-EM data has allowed us to determine that its conserved core is a hallmark fold preserved in the dsRNA virus lineage.