Functional role of the cytoplasmic tail domain of the major envelope fusion protein of group II baculoviruses.
F proteins from baculovirus nucleopolyhedrovirus (NPV) group II members are the major budded virus (BV) viral envelope fusion proteins. They undergo furin-like proteolysis processing in order to be functional. F proteins from different baculovirus species have a long cytoplasmic tail domain (CTD), ranging from 48 (Spodoptera litura multicapsid NPV [MNPV]) to 78 (Adoxophyes honmai NPV) amino acid (aa) residues, with a nonassigned function. This CTD is much longer than the CTD of GP64-like envelope fusion proteins (7 aa), which appear to be nonessential for BV infectivity. Here we have investigated the functional role of the CTD of Helicoverpa armigera single-capsid NPV (HearNPV), a group II NPV. We combined a newly constructed HearNPV f-null bacmid knockout-repair system and an Autographa californica MNPV (AcMNPV) gp64-null bacmid knockout-pseudotype system with mutation and rescue experiments to study the functional role of the baculovirus F protein CTD. We show that except for the 16 C-terminal aa, the HearNPV F CTD is essential for virus spread from cell to cell. In addition, the CTD of HearNPV F is involved in BV production in a length-dependent manner and is essential for BV infectivity. The tyrosine residue Y658, located 16 aa from the C terminus, seems to be critical. However, HearNPV F without a CTD still rescues the infectivity of gp64-null AcMNPV BV, indicating that the CTD is not involved in processing and fusogenicity. Altogether, our results indicate that the F protein is essential for baculovirus BV infectivity and that the CTD is important for F protein incorporation into BV.
Long
Gang
G
Department of Virology, Wageningen University, Binnenhaven 11, 6709 PD Wageningen, The Netherlands.
Pan
Xiaoyu
X
Westenberg
Marcel
M
Vlak
Just M
JM
D000595:Amino Acid Sequence; D000818:Animals; D005816:Genetic Complementation Test; D007915:Lepidoptera; D008969:Molecular Sequence Data; D009154:Mutation; D017924:Nucleopolyhedroviruses / Q000235:genetics / Q000502:physiology*; D017434:Protein Structure, Tertiary; D018411:Spodoptera; D014162:Transfection; D014759:Viral Envelope Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D014760:Viral Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*
D014759:Viral Envelope Proteins; D014760:Viral Fusion Proteins