Size and structure of the genome of infectious pancreatic necrosis virus

The genome of infectious pancreatic necrosis virus consists of two segments of dsRNA, in equimolar amounts, with molecular weights of 2.5 X 10(6) and 2.3 X 10(6) daltons, as determined by polyacrylamide gel electrophoresis and autoradiography. The viral RNA was resistant to ribonuclease, and in sucrose gradient it co-sedimented at 14S with RNase resistant RNA from virus infected cells. Upon denaturation in 98% formamide, the viral genome sedi-mented at 24S in formamide sucrose gradient and became sensitive to RNase. Denatured 24S viral RNA did revert to its undenatured 14S form upon recentrifugation in aquaeous sucrose gradient (0.1 M NaCL), but co-sedimented with the denatured large size class of reovirus 25S RNA. The same results were obtained if the native viral RNA was pre-treated with ribonuclease before denaturation, indicating the absence of exposed single strainded regions in the viral genome. Since infectious pancreatic necrosis virus contains only two dsRNA segments it does not belong to the family Reoviridae and may represent a new group of viruses.