Mutational analysis of the feline immunodeficiency virus matrix protein

To study the process of feline immunodeficiency virus (FIV) assembly, we ex amined the suitability of the vaccinia vector system to reproduce FIV parti cle formation. To this end, we constructed a recombinant vaccinia virus car rying the FIV gag gene. Biochemical and electron microscopy analyses of cel ls infected with this recombinant virus sf:owed that the FIV Gag polyprotei n self-assembled into lentivirus-like particles that were released into the culture medium. As a first step in the identification of molecular determi nants in FIV Gag that are involved in virus assembly, we performed a site-d irected mutagenesis analysis of the N-terminal matrix (MA) domain of the FI V Gag precursor. To this end, a series of amino acid substitutions and smal l in-frame deletions were introduced into the FIV MA and the mutated FIV ga g gene constructs were expressed by means of the vaccinia system. Character ization of the assembly phenotype of these FIV Gag mutants led to the ident ification of amino acidic regions within the MA domain that are necessary f or efficient transport of the Gag precursor to the plasma membrane and part icle assembly. Our results reveal the role that the FIV MA plays in virus m orphogenesis and contribute to the understanding of the assembly process in non-primate lentiviruses. (C) 2001 Elsevier Science B.V. All rights reserv ed.