Related Experiment Video
Updated: May 20, 2026
Arbovirus Infections As Screening Tools for the Identification of Viral Immunomodulators and Host Antiviral Factors
Published on: September 13, 2018
Identification and characterization of host factors interacting with Bombyx mori nucleopolyhedrovirus ORF8
Wonkyung Kang1, Susumu Katsuma, Noriko Matsuda-Imai
1Molecular Entomology Laboratory, RIKEN ASI, 2-1 Hirosawa, Wako, 351-0198, Japan.
Abstract:
The orf8 gene (Bm8) in Bombyx mori nucleopolyhedrovirus (BmNPV) is one of 17 genes unique to group I NPVs and is expressed as an early gene. We have reported that Bm8 may play an important role during viral infection and that Bm8 protein co-localized with IE1 to specific nuclear foci throughout infection. It was also demonstrated that both IE1 and BmNPV hr facilitate this localization of Bm8. To investigate further, host proteins interacting with Bm8 were screened using a yeast two-hybrid system. We identified 6 host clones as Bm8-interacting partners from three cDNA libraries derived from BmN cells or B. mori larvae. Further assays showed that the N-terminal region of Bm8 is important for the interaction with most host clones and that two of the clones can associate with IE1. Cloning and sequencing of full-length cDNAs revealed that most of the clones potentially encode either membrane-bound proteins or secreted proteins. Quantitative RT-PCR analysis revealed that some of these host genes were slightly induced during the early stage of infection in BmN cells, and that the expression of all genes was markedly reduced during the late stage of infection. Generation of mutant BmNPVs over-expressing these host genes also identified a gene that potentially functions as a negative factor during BmNPV infection. These features of Bm8-interacting host proteins strongly support that Bm8 is a multifunctional protein involved in multiple signaling pathways in host cells.
Insights
The Bombyx mori nucleopolyhedrovirus (BmNPV) orf8 gene (Bm8) interacts with host proteins, influencing viral infection. These interactions suggest Bm8 is a multifunctional protein involved in host cell signaling pathways.
Area of Science:
- Virology
- Molecular Biology
- Insect Pathology
Background:
- The orf8 gene (Bm8) is unique to group I nucleopolyhedroviruses (NPVs) and expressed early during infection.
- Bm8 protein co-localizes with IE1 to nuclear foci, facilitated by IE1 and BmNPV hr.
- Bm8's role in viral infection suggests interactions with host factors.
Purpose of the Study:
- To identify host proteins interacting with the Bm8 protein.
- To elucidate the functional significance of Bm8-host protein interactions during BmNPV infection.
Main Methods:
- Yeast two-hybrid screening using cDNA libraries from BmN cells and B. mori larvae.
- Interaction assays to confirm Bm8 and host protein binding, including N-terminal region analysis.
- Quantitative RT-PCR to analyze host gene expression during infection.
- Generation of mutant BmNPVs to assess host gene function.
Main Results:
- Six host proteins were identified as Bm8 interaction partners.
- The N-terminal region of Bm8 is crucial for interaction with most partners.
- Two host partners also associate with the viral protein IE1.
- Host gene expression is modulated during infection, with some induced early and suppressed late.
- A specific host gene was identified as a negative factor in BmNPV infection.
Conclusions:
- Bm8 interacts with multiple host proteins, indicating its multifunctional nature.
- These interactions likely mediate Bm8's role in modulating host cell signaling pathways during viral infection.
- Bm8's involvement in diverse host-pathogen interactions is a key aspect of BmNPV pathogenesis.
