Analysis of a human immunodeficiency virus type 1 gag mutant with an engineered 110-amino-acid insertion in the matrix protein domain

A human immunodeficiency virus (HIV) matrix (MA) protein mutant was constru cted by duplication of 107 codons of the HIV-1 MA domain. This MA protein d uplication mutant (MAII) still could assemble and process particles, had a wild-type (wt) HIV particle density, and possessed reverse transcriptase ac tivity of about 80% of the wild type virus level. The incorporation of HIV Env and viral RNA genome was not greatly affected. The MAII was noninfectio us or poorly infectious, however, when pseudotyped with an amphotropic muri ne leukemia virus envelope protein or with the HIV envelope protein. Althou gh the MAII mutant displayed an immunofluorescence staining pattern similar to that of the wild type virus, subcellular fractionation studies indicate d that the membrane association of MAII Gag precursors was unstable under h igh-salt conditions. Electron microscopic studies showed that the mutant ha d a decreased density of particle cores compared with that of the wild type virus, suggesting an altered arrangement of the packed proteins. As this i nsertion in the MA gene caused no major effects on virus assembly implies t hat the HIV-1 gag has the potential to adapt large insertions of extra codi ng sequences without loss of the ability to direct particle assembly and re lease. J. Med. Virol. 61:423-432, 2000. (C) 2000 WiIey-Liss, Inc.