THE HIV-1 MATRIX DOMAIN OF GAG IS REQUIRED FOR VPU RESPONSIVENESS DURING PARTICLE RELEASE

HIV-1 viral protein U (Vpu) facilitates virus particle release. To det ermine whether Gag is sufficient for generation of a target for Vpu-me diated particle release, we expressed HIV-1 Gag protein in the absence of the other viral genes. The resulting particles were still Vpu resp onsive. Mutational analysis of Gag indicated that the matrix domain (M A) is required for Vpu responsiveness. However, additional mutations i n other domains of Ga, which affect the formation of stable virus part icles, also abrogate Vpu responsiveness on total Gag release. Coexpres sion of the wild-type gag gene-and a gag mutant lacking the MA domain renders the MA(-) mutant Vpu responsive. This indicates that Gag molec ules lacking MA are still incorporated into particles through associat ion with wild-type Gag molecules and that the resulting composite part icles are sufficient for Vpu-mediated exit. (C) 1997 Academic Press.