Characterization of the RNA-binding regions in protein p36 of Heliothis armigera cypovirus 14

Interactions among Dendrolimus punctatus cypovirus proteins and identification of the genomic segment encoding its A-spike

Revealing the interactions among cypovirus proteins would facilitate our understanding of the replication and assembly of this virus. In the present study, interactions among proteins encoded by the 10 segments of Dendrolimus punctatus cypovirus (DpCPV) were identified using yeast two-hybrid (Y2H) and far-Western blotting assays. In total, 24 pairs of interactions were detected. Twelve pairs of one-direction interactions, four pairs of binary interactions and four pairs of self-associations were identified in the Y2H assays. Another four pairs of interactions were identified by far-Western blotting. The interactions between the methyltransferase domain of the turret protein (VP3) and VP4 as well as between polyhedrin and VP4 were further confirmed by far-Western blotting and pull-down assays, respectively. In addition, immunogold labelling showed that the A-spike of DpCPV is formed by VP4. In conclusion, we obtained a protein-protein interaction network of DpCPV and showed that its A-spike is formed by VP4 encoded by genomic segment 6.

Characterization of the complete genome segments from BmCPV-SZ, a novelBombyx moricypovirus 1 isolate

A novel Bombyx mori cypovirus 1 isolated from infected silkworm larvae and tentatively assigned as Bombyx mori cypovirus 1 isolate Suzhou (BmCPV-SZ). The complete nucleotide sequences of genomic segments S1–S10 from BmCPV-SZ were determined. All segments possessed a single open reading frame; however, bioinformatic evidence suggested a short overlapping coding sequence in S1. Each BmCPV-SZ segment possessed the conserved terminal sequences AGUAA and GUUAGCC at the 5′ and 3′ ends, respectively. The conserved A/G at the –3 position in relation to the AUG codon could be found in the BmCPV-SZ genome, and it was postulated that this conserved A/G may be the most important nucleotide for efficient translation initiation in cypoviruses (CPVs). Examination of the putative amino acid sequences encoded by BmCPV-SZ revealed some characteristic motifs. Homology searches showed that viral structural proteins VP1, VP3, and VP4 had localized homologies with proteins of Rice ragged stunt virus , a member of the genus Oryzavirus within the family Reoviridae. A phylogenetic tree based on RNA-dependent RNA polymerase sequences demonstrated that CPV is more closely related to Rice ragged stunt virus and Aedes pseudoscutellaris reovirus than to other members of Reoviridae, suggesting that they may have originated from common ancestors.

The nuclear localization signal of the NS1 protein is essential for Periplaneta fuliginosa densovirus infection

The regulatory protein NS1 is a key molecule in life cycle of Periplaneta fuliginosa densovirus (PfDNV). When we ectopically expressed the PfDNV NS1 protein in non-P. fuliginosa insect cells, the NS1 protein could not enter the nucleus and remained in the cytosol. However, the NS1 was localized to both the cytosol and nucleus of cockroach hemocyte cells. So we investigated the abilities of the potential nuclear localization signal (NLS) of P. fuliginosa Densovirus non-structural protein 1 (NS1) to translocate NS1 and a carrier protein to the nucleus following transfection into insect cells. Possible nuclear localization sequences were chosen from the NS1 on the basis of the presence of basic residues, which is a common theme in most of the previously identified targeting peptides. Nuclear localization activity was found within the residues 252-257 (RRRRRR) of the NS1, while replacement of a single arginine in this region with glycine abolished it. The targeting activity was enhanced with the arginine residues added.