Bombyx mori nucleopolyhedrovirus (BmNPV) is extremely harmful to the silk industry. The polyhedrin, which encodes the polyhedrin (Polh), can be expressed at ultra-high levels and form occlusion bodies in the nucleus, embedding the progeny virus within it. However, the detailed mechanism by which polyhedrin is transported into the host cell nucleus remains unknown. Clarifying the nuclear import mechanisms of viral proteins can help us develop better prevention and treatment measures against baculoviruses. This study employed molecular cloning, co-immunoprecipitation, and immunofluorescence to analyze in detail the expression pattern of the highly expressed polyhedrin in the very late stage of the virus, and further revealed that the host protein importin α participates in the nuclear import of polyhedrin through protein interactions. This study provides a reference for further elucidating the nuclear import mechanisms of the baculovirus proteins including polyhedrin that can enter the nucleus.
Nucleopolyhedroviruses/metabolism* ; Active Transport, Cell Nucleus ; Animals ; Bombyx/virology* ; alpha Karyopherins/metabolism* ; Cell Nucleus/metabolism* ; Viral Structural Proteins/metabolism* ; Occlusion Body Matrix Proteins

Human epidermal growth factor (hEGF) can be applied in the treatment of surgical trauma (burns, scalds), tissue repair, skin moisturizing, beauty, skincare, etc. However, the low expression and high cost limit the application of hEGF. In order to improve the expression level of hEGF and reduce the production cost, considering the high expression of polyhedrin, this study fused a partial sequence of polyhedrin with hEGF and expressed the fused sequence by using a silkworm baculovirus expression vector system. In view of the small molecular weight of hEGF, we connected hEGF genes in series and optimized the codons to construct multiple fusion expression vectors by fusing different partial sequences of polyhedrin at the N-terminus. The results showed that through the above strategy, the protein expression level of hEGF was significantly increased. The expression vector containing three concatenated hEGF genes with optimized codons and fused with the sequence encoding 25 or 35 residues at the N-terminus of polyhedrin showed the highest expression level.
Humans ; Epidermal Growth Factor/biosynthesis* ; Genetic Vectors/genetics* ; Recombinant Fusion Proteins/biosynthesis* ; Animals ; Bombyx/metabolism* ; Occlusion Body Matrix Proteins/genetics* ; Nucleopolyhedroviruses/genetics* ; Amino Acid Sequence