Mechanisms used by multisegmented dsRNA animal viruses in counting and selecting genomic segments during replication (360G-Wellcome-089310_Z_09_Z)

Recent advances in reverse genetics of dsRNA viruses have shed light on some aspects of genome packaging, yet the question of genome segment counting is not resolved. There is no available in vitro re-assembly system for animal dsRNA viruses, mostly because of the complexity of the viral protein-protein, protein-RNA and RNA-RNA interactions involved in virus particle formation. Genomic RNA may play pivotal roles in the assembly and sorting of genome segments. The proposed research project will investigate the mechanisms of segmented genome encapsidation by animal dsRNA viruses using 2 model systems: avian reovirus and infectious bursal disease virus (IBDV). These viruses are important poultry pathogens worldwide, and are convenient and relevant models for understanding dsRNA virus assembly. Avian reovirus with its genomic segments has much in common with other mammalian reoviruses and rotaviruses, while the structure of IBDV has been extensively characterized, although nothing is known about the mechanisms of its RNA packaging. Moreover, recent experimental data suggest that IBDV two-segmented genomic RNA packaging lacks the tight selective (1control typical for rotaviruses and reoviruses, and comparative studies may help our further understanding of the structural basis for selective packaging of dsRNA viral genomes. The specific objectives of the project are: 1) To map specific protein-RNA and RNA-RNA interactions involved in virus genome packaging; 2) To establish in vitro virus assembly assays based on the data from objective 1 and to characterize assembly intermediates in real-time. 3) To develop in vivo assembly assays for our model viruses and to test the predictions from the in vitro studies of the virus particle formation and genome encapsidation.