Jiv90 is a fragment of the DnaJ protein in eukaryotes and in J-domain protein interacting with viral protein (Jiv) located in the N terminal region of the pestivirus viral polypeptide. The viral protein interacts stably with non structural (NS) protein NS2, causing a conformational change in NS2-NS3 and stimulates NS2-NS3 cleavage in trans. Cleavage of NS2-NS3 increases cytopathogenicity and consequently aids viral replication. Jiv therefore acts as a regulating cofactor for NS2 auto-protease. The efficient release of NS3 from the viral polypeptide by Jiv is considered crucial to the pestivirus cytopathogenicity [1]. In eukaryotes, it usually lies 40 residues downstream of DnaJ family Pfam:PF00226. However, the function in eukaryotes is still unknown.

1: Cell-derived sequences in the N-terminal region of the polyprotein of a cytopathogenic pestivirus. Muller A, Rinck G, Thiel HJ, Tautz N; J Virol. 2003;77:10663-10669. PMID:12970452

2: A cellular J-domain protein modulates polyprotein processing and cytopathogenicity of a pestivirus. Rinck G, Birghan C, Harada T, Meyers G, Thiel HJ, Tautz N; J Virol. 2001;75:9470-9482. PMID:11533209