Nuclear Accumulation of Bm65 Aggregate Is Blocked by Mutations in the Nuclear Export Sequence of Bm65.

A nuclear export signal (NES) is a cluster of hydrophobic amino acids that can maintain the dynamic shuttling of target proteins between the nucleus and cytoplasm. Bioinformatics analysis showed that the hydrophobic region of PLLLHKFLLA in Bm65 is very likely to be an NES and may be involved in the production of infectious virions. In this study, we generated several mutations in PLLLHKFLLA of Bm65, which were further used to generate recombinant viruses to study their roles in viral propagation. Subcellular analysis revealed that the PLLLHKFLLA sequence was an NES involved in the dynamic transport of Bm65. Mutations in the hydrophobic region could block the formation and accumulation of Bm65 aggregates, resulting in a uniform distribution of Bm65 in BmN cells. The ribosomal protein L13 (RPL13) of silkworms was previously reported to interact with Bm65. Here, intracellular co-localization analysis showed that the interaction between Bm65 and RPL13 was regulated by the PLLLHKFLLA of Bm65. In summary, the interaction between Bm65 and RPL13 is essential for the production and accumulation of Bm65 aggregates and may play an important role in the regulation of viral propagation.