Six mutants that differ in the extent of their carboxy- terminal sequences and two deletion mutants of the gag gene of HIV-1 have been characterized morphologically following their expression in Spodoptera Jrugiperda cells using recombinant baculoviruses. Electron microscopy has revealed distinct morphological forms of the Gag protein that can be classified as either (i) particulate, three-dimensional, spherical or tubular shells or (ii) nonparticulate, two-dimensional, flat, curved or convoluted sheets. Progressive truncation of the carboxy terminus of Gag was accompanied by changes in the morphology and formation of spherical particles from predominantly C-type assembly and budding at the plasma membrane, through B-type intracytoplasmic assembly, to A-type assembly with budding mainly into cytoplasmic vacuoles. Deletions within the Pr24 CA domain of Gag abolished particle formation but retained association of the protein with the plasma membrane. All of the observed morphologies of the mutant Gag proteins could be accommodated within an icosahedral model for the organization of spherical particles and a basic hexagonal arrangement of assembled Gag protein monomers.
ChazalN., CarrièreC., GayB., BoulangerP.1994; Phenotypic characterization of insertion mutants of the human immunodeficiency virus type 1 Gag precursor expressed in recombinant baculovirus-infected cells. Journal of Virology 68:111–122
ClavelF., OrensteinJ. M.1990; A mutant of human immunodeficiency virus with reduced RNA packaging and abnormal particle morphology. Journal of Virology 64:5230–5234
FäckeM., JanetzkoA., ShoemanR. L., KräusslichH. -G.1993; A large deletion in the matrix domain of the human immunodeficiency virus gag gene redirects virus particle assembly from the plasma membrane to the endoplasmic reticulum. Journal of Virology 67:4972–4980
GorelickR. J., NigidaS. M.JrBessJ. W.JrArthurL. O., HendersonL. E., ReinA.1990; Noninfectious human immunodeficiency virus type 1 mutants deficient in genomic RNA. Journal of Virology 64:3207–3211
GöttlingerH. G., SodroskiJ. G., HaseltineW. A.1989; Role of capsid precursor processing and myristoylation in morphogenesis and infectivity of human immunodeficiency virus type 1. Proceedings of the National Academy of Sciences U.S.A: 865781–5785
GöttlingerH. G., DorfmanT., SodroskiJ. G., HaseltineW. A.1991; Effect of mutations affecting the p6 gag protein on human immunodeficiency virus particle release. Proceedings of the National Academy of Sciences U.S.A: 883195–3199
GriefC., NermutM. V., HockleyD. J.1994; A morphological and immunolabelling study of freeze-substituted human and simian immunodeficiency viruses. Micron 25:119–128
HoshikawaN., KojimaA., YasudaA., TakayashikiE., MusakoS., ChibaJ., SataT., KurataT.1991; Role of the gag and pol genes of human immunodeficiency virus in the morphogenesis and maturation of retrovirus-like particles expressed by recombinant vaccinia virus: an ultrastructural study. Journal of General Virology 72:2509–2517
JowettJ. B. M., HockleyD. J., NermutM., JonesI. M.1992; Distinct signals in human immunodeficiency virus type 1 Pr55 necessary for RNA binding and particle formation. Journal of General Virology 73:3079–3086
KaracostasV., NagashimaK., GondaM. A., MossB.1989; Human immunodeficiency virus-like particles produced by a vaccinia virus expression vector. Proceedings of the National Academy of Sciences U.S.A: 868964–8967
LubanJ., LeeC., GoffS. P.1993; Effect of linker insertion mutations in the human immunodeficiency virus type 1 gag gene on activation of viral protease expressed in bacteria. Journal of Virology 67:3630–3634
MarxP. A., MunnR. J., JoyK. I.1988; Computer emulation of thin section electron microscopy predicts an envelope-associated icosadeltahedral capsid for human immunodeficiency virus. Laboratory Investigation 58:112–118
MatsuuraY., PosseeR. D., OvertonH. A., BishopD. H. L.1987; Baculovirus expression vectors: the requirements for high level expression of proteins, including glycoproteins. Journal of General Virology 68:1233–1250
NermutM. V., FrankH., SchäferW.1972; Properties of mouse leukemia virus. III. Electron microscopic appearance as revealed after conventional preparation techniques as well as freeze-drying and freeze-etching. Virology 49:345–358
NermutM. V., NicolA.1989; Colloidal gold immunoreplica method. In Colloidal Gold: Principles, Methods and Applications1 pp 349–373HayatM. A. Edited by San Diego: Academic Press;
NermutM. V., GriefC., HashmiS., HockleyD. J.1993; Further evidence of icosahedral symmetry in human and simian immunodeficiency virus. AIDS Research and Human Retroviruses 9:929–938
NermutM. V., HockleyD. J., JowettJ. B. M., JonesI. M., GarreauM., ThomasD.1994; Fullerene-like organization of HIV Gag-protein shell in virus-like particles produced by recombinant baculovirus. Virology 198:288–296
OvertonH. A., FujiiY., PriceI. R., JonesI. M.1989; The protease and gag gene products of the human immunodeficiency virus: authentic cleavage and post-translational modification in an insect cell expression system. Virology 170:107–116
RheeS. S., HunterE.1990; A single amino acid substitution within the matrix protein of a type D retrovirus converts its morphogenesis to that of a type C retrovirus. Cell 63:77–86
SpearmanP., WangJ. -J., Vander HeydenN., RatnerL.1994; Identification of human immunodeficiency virus type 1 Gag protein domains essential to membrane binding and particle assembly. Journal of Virology 68:3232–3242
SummersM. D., SmithG. E.1987A Manual of Methods for Baculovirus Vectors and Insect Cell Culture procedures. Texas Agricultural Experimental Research Station;1555
Van Der WilkF., Van LentJ. W. M., VlakJ. M.1987; Immunogold detection of polyhedrin, plO and virion antigens in Autographa californica nuclear polyhedrosis virus-infected Spodop- tera frugiperda cells. Journal of General Virology 68:2615–2623
Von PoblotzkiA., WagnerR., NiedrigM., WannerG., WolfH., ModrowS.1993; Identification of a region in the Pr55gag-polyprotein essential for HIV-1 particle formation. Virology 193:981–985
YuX., YuanX., MatsudaZ., LeeT. -H., EssexM.1992a; The matrix protein of human immunodeficiency virus type 1 is required for incorporation of viral envelope protein into mature virions. Journal of Virology 66:4966–4971
YuX., YuQ. -C., LeeT. -H., EssexM.1992b; The C terminus of human immunodeficiency virus type 1 matrix protein is involved in early steps of the virus life cycle. Journal of Virology 66:5667–5670
YuanX., YuX., LeeH. -T., EssexM.1993; Mutations in the N- terminal region of human immunodeficiency virus type 1 matrix protein block intracellular transport of the Gag precursor. Journal of Virology 67:6387–6394