Autographa californica multiple nucleopolyhedrovirus nucleocapsid protein BV/ODV-C42 mediates the nuclear entry of P78/83.
Autographa californica multiple nucleopolyhedrovirus (AcMNPV) BV/ODV-c42 (orf101; c42), which encodes a 41.5-kDa viral nucleocapsid protein with a putative nuclear localization signal (NLS) motif at the C terminus, is a highly conserved gene among members of the Baculoviridae family. C42 is demonstrated to be essential for AcMNPV propagation and can bind to nucleocapsid protein P78/83, a viral activator for the actin-related protein 2/3 (ARP2/3) complex to initiate nuclear actin polymerization, which is essential for viral nucleocapsid morphogenesis during AcMNPV infection. Here, we report the identification of a novel pathway through which c42 functions in nucleocapsid assembly. Cotransfection of Sf9 cells with c42 and p78/83 plasmids demonstrated that C42 was capable of recruiting P78/83 to the nuclei of uninfected cells and that the NLS motif of C42 was essential for this process. To validate this nuclear relocation mode in bacmid-transfected cells, a c42-disrupted bacmid (vAc(c42ko-gfp)) and rescued bacmids with wild-type c42 (vAc(c42res-gfp)) or with NLS coding sequence-mutated c42 (vAc(c42nls-gfp)) were prepared. By immuno-staining, P78/83 was found to be localized in the cytoplasm of either vAc(c42ko-gfp)- or vAc(c42nls-gfp)-transfected cells, whereas P78/83 was relocated to the nuclei of vAc(c42res-gfp)-transfected cells. Furthermore, F-actin-specific staining confirmed that there was no actin polymerization activity in the nuclei of either vAc(c42ko-gfp)- or vAc(c42nls-gfp)-transfected cells, which might be attributed to the absence of nuclear P78/83, an activator of the ARP2/3 complex to initiate nuclear actin polymerization. We therefore hypothesize a mode of action where C42 binds to P78/83 in the cytoplasm to form a protein complex and cotransports to the nucleus under the direction of the NLS motif in C42 during AcMNPV infection.
Wang
Yun
Y
State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China. chenxw@pentium.whiov.ac.cn
Wang
Qian
Q
Liang
Changyong
C
Song
Jianhua
J
Li
Ni
N
Shi
Hui
H
Chen
Xinwen
X
D051376:Actin-Related Protein 2-3 Complex / Q000378:metabolism; D021581:Active Transport, Cell Nucleus; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D007313:Insecta; D019913:Nuclear Localization Signals; D019590:Nucleocapsid Proteins / Q000378:metabolism*; D017924:Nucleopolyhedroviruses / Q000737:chemistry / Q000502:physiology*; D014759:Viral Envelope Proteins
D051376:Actin-Related Protein 2-3 Complex; D002352:Carrier Proteins; D019913:Nuclear Localization Signals; D019590:Nucleocapsid Proteins; D014759:Viral Envelope Proteins