Subnanometer-resolution structures of the grass carp reovirus core and virion.

Grass carp reovirus (GCRV) is a member of the Aquareovirus genus of the family Reoviridae, a large family of double-stranded RNA (dsRNA) viruses infecting plants, insects, fishes and mammals. We report the first subnanometer-resolution three-dimensional structures of both GCRV core and virion by cryoelectron microscopy. These structures have allowed the delineation of interactions among the over 1000 molecules in this enormous macromolecular machine and a detailed comparison with other dsRNA viruses at the secondary-structure level. The GCRV core structure shows that the inner proteins have strong structural similarities with those of orthoreoviruses even at the level of secondary-structure elements, indicating that the structures involved in viral dsRNA interaction and transcription are highly conserved. In contrast, the level of similarity in structures decreases in the proteins situated in the outer layers of the virion. The proteins involved in host recognition and attachment exhibit the least similarities to other members of Reoviridae. Furthermore, in GCRV, the RNA-translocating turrets are in an open state and lack a counterpart for the sigma1 protein situated on top of the close turrets observed in mammalian orthoreovirus. Interestingly, the distribution and the organization of GCRV core proteins resemble those of the cytoplasmic polyhedrosis virus, a cypovirus and the structurally simplest member of the Reoviridae family. Our results suggest that GCRV occupies a unique structure niche between the simpler cypoviruses and the considerably more complex mammalian orthoreovirus, thus providing an important model for understanding the structural and functional conservation and diversity of this enormous family of dsRNA viruses.

ANKRD1, the gene encoding cardiac ankyrin repeat protein, is a novel dilated cardiomyopathy gene.

OBJECTIVES: We evaluated ankyrin repeat domain 1 (ANKRD1), the gene encoding cardiac ankyrin repeat protein (CARP), as a novel candidate gene for dilated cardiomyopathy (DCM) through mutation analysis of a cohort of familial or idiopathic DCM patients, based on the hypothesis that inherited dysfunction of mechanical stretch-based signaling is present in a subset of DCM patients. BACKGROUND: CARP, a transcription coinhibitor, is a member of the titin-N2A mechanosensory complex and translocates to the nucleus in response to stretch. It is up-regulated in cardiac failure and hypertrophy and represses expression of sarcomeric proteins. Its overexpression results in contractile dysfunction. METHODS: In all, 208 DCM patients were screened for mutations/variants in the coding region of ANKRD1 using polymerase chain reaction, denaturing high-performance liquid chromatography, and direct deoxyribonucleic acid sequencing. In vitro functional analyses of the mutation were performed using yeast 2-hybrid assays and investigating the effect on stretch-mediated gene expression in myoblastoid cell lines using quantitative real-time reverse transcription-polymerase chain reaction. RESULTS: Three missense heterozygous ANKRD1 mutations (P105S, V107L, and M184I) were identified in 4 DCM patients. The M184I mutation results in loss of CARP binding with Talin 1 and FHL2, and the P105S mutation in loss of Talin 1 binding. Intracellular localization of mutant CARP proteins is not altered. The mutations result in differential stretch-induced gene expression compared with wild-type CARP. CONCLUSIONS: ANKRD1 is a novel DCM gene, with mutations present in 1.9% of DCM patients. The ANKRD1 mutations may cause DCM as a result of disruption of the normal cardiac stretch-based signaling.