The importance of the NP: VP35 ratio in Ebola virus nucleocapsid formation.

Ebola virus VP35 is a cofactor of the viral RNA polymerase complex and, together with NP and VP24, is an essential component for nucleocapsid formation. In the present study, we examined the interactions between VP35 and NP and found that VP35 interacts with helical NP-RNA complexes through the C-terminus of NP. We also found that coexpression of excess VP35 with NP reduced the yields of NP-RNA complexes purified by CsCl gradient ultracentrifugation and inhibited the formation of the NP-induced inclusion bodies that typically form in Ebola virus-infected cells. These findings suggest that the NP to VP35 ratio is important in the Ebola virus replication cycle and advance our knowledge of nucleocapsid morphogenesis.