The BRO proteins of Bombyx mori nucleopolyhedrovirus are nucleocytoplasmic shuttling proteins that utilize the CRM1-mediated nuclear export pathway.
The BRO proteins of Bombyx mori nucleopolyhedrovirus (BmNPV) display a biphasic pattern of intracellular localization during infection. At early times, they reside in the nucleus but then show both cytoplasmic and nuclear localization as the infection proceeds. Therefore, we examined the possibility of nuclear export. Using inhibitors, we reveal that BmNPV BRO proteins shuttle between the nucleus and cytoplasm. Mutations on the leucine-rich region of BRO proteins resulted in nuclear accumulation of transiently expressed proteins, suggesting that this region functions as a CRM1-dependent nuclear export signal (NES). On the contrary, mutant BRO-D with an altered NES did not show nuclear accumulation in infected cells, although protein production seemed to be reduced. RT-PCR analysis showed that the lower level of protein production was due to a reduction in RNA synthesis. Taken together, our results suggest that BRO proteins are nucleocytoplasmic shuttling proteins that utilize the CRM1-mediated nuclear export pathway.
Molecular Entomology Laboratory, RIKEN, 2-1 Hirosawa, Wako 351-0198, Japan. wkkang@riken.jp
WonKyung
W
Kang
Masaaki
M
Kurihara
Shogo
S
Matsumoto
D000595:Amino Acid Sequence; D000818:Animals; D012831:Bombyx / Q000821:virology*; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D016384:Consensus Sequence; D003593:Cytoplasm / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D028884:Karyopherins / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins / Q000235:genetics / Q000378:metabolism*; D017924:Nucleopolyhedroviruses / Q000378:metabolism*; D012367:RNA, Viral / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D014764:Viral Proteins / Q000378:metabolism*; D000097606:Exportin 1 Protein
D028884:Karyopherins; D029543:Nucleocytoplasmic Transport Proteins; D012367:RNA, Viral; D018160:Receptors, Cytoplasmic and Nuclear; D014764:Viral Proteins; D000097606:Exportin 1 Protein