Some Properties of Influenza Virus Nucleocapsids

Abstract

Nucleocapsids released from influenza virions by sodium deoxycholate sedimented heterogeneously in sucrose gradients. Highly infectious virus (complete) preparations yielded nucleocapsids with peak distributions at 64 and 56 S ; von Magnus type virus (incomplete) lacked 64 S nucleocapsids. Treatment of influenza virus nucleocapsids with pancreatic ribonuclease rendered the associated viral ribonucleic acid (RNA) molecules acid-soluble, indicating that capsid proteins do not completely surround the viral RNA's. However, the capsid proteins remained associated after enzymatic hydrolysis of the RNA, as judged by persistently high sedimentation rates. Sedimentation rates of viral nucleocapsids reflected the sedimentation rates of the associated RNA's: 64 S nucleocapsids contained 18 S RNA, whereas 56 S nucleocapsids contained 15 S RNA, although in both cases RNA's sedimenting at 4 to 13 S were also recovered. Furthermore, just as incomplete virions lacked 64 S nucleocapsids, they also lacked 18 S RNA. These findings support the hypothesis that the influenza virus genome is divided among several distinct pieces of RNA.