Matrix-induced inhibition of membrane binding contributes to human immunodeficiency virus type 1 particle assembly defects in murine cells

Defective human immunodeficiency virus type 1 (HIV-1) assembly in murine cells is accompanied by poor plasma membrane binding and proteolytic processing of the HIV-1 Gag precursor. Here, we show that such defects are induced by the propensity of the HIV-1 MA globular head to inhibit membrane binding and particle assembly, particularly at the low expression levels observed in murine cells. Simple additions to or deletion of the MA globular head can improve the yield of infectious virions from murine cells by > 50-fold. Expression level and autoinhibition can be important confounding variables in studies of HIV-1 assembly and contribute to defects encountered in murine cells.