The smallest RNA segment (S10) of bluetongue virus (an orbivirus, family Reoviridae) encodes two closely related nonstructural proteins, the 229-amino-acid (aa) NS3 and the 216-aa NS3A. The proteins are found in glycosylated and nonglycosylated forms in infected cells (X. Wu, H. Iwata, S.-Y. Chen, R. W. Compans and P. Roy J. Virol. 66:7104–7112, 1992). The NS3/NS3A proteins have two hydrophobic domains (aa 118 to 141 and 162 to 182) and two potential asparagine-linked glycosylation sites (aa 63 and 150), one of which is located between the hydrophobic domains. To determine whether these features were used in the mature protein forms, we generated a series of mutants of the S10 gene and expressed them by using the vaccinia virus T7 polymerase transient-expression system. Our data indicate that both hydrophobic domains of NS3 span the cell membrane and that only the site at aa 150 is responsible for N-linked glycosylation of the NS3 proteins.

The polyhedrin gene (polh) of a characteristically distinct Spodoptera litura nuclear polyhedrosis virus isolate (SIMNPV) is identified in the HindIII-F fragment of the viral DNA. The nucleotide sequence of the 1057 base pair (bp) region of this fragment contains an open reading frame (ORF) without any intervening sequence for coding a polypeptide of 246 amino acids. Analysis of the nucleotide sequence and deduced amino acid sequence indicate that this has more than 70% sequence identity to known polyhedrins. The coding region is preceded by an AT rich region containing the conserved late promoter motif TAAG. The upstream promoter and coding regions of this polh gene are more similar to polh of the NPVs of Spodoptera frugiperda (Sf), Spodoptera exigua (Se) and Panolis flamea (Pf).

No abstract

Genome segment 9 of bluetongue virus serotype 10 encodes the minor protein VP6. The protein is abundant with basic residues particularly in two regions of the carboxy half of the molecule. A series of amino-and carboxy-terminal deletion mutants was expressed in mammalian cells by using a vaccinia virus T7 polymerasedriven transient expression system, and the intracellular fate of the products was monitored by both immunofluorescence staining and cell fractionation techniques. Data obtained indicated clearly that VP6 has nuclear transportation signals which may be correlated with positively charged domains of the molecule. In the intact molecule, though, these signals are masked and the protein is retained in the cytoplasm. The biochemical and immunofluorescence data obtained indicate that sequences in the region of residues 33 to 80 of the 328-aminoacid protein are required for the retention of VP6 within the cell cytoplasm while amino acids 303 to 308 in the carboxy-terminal half of the molecule appear to possess nuclear localization capabilities.

No abstract