Modification of virus infectivity by cytoplasmic tail of HIV-1 TM protein.

Envelope glycoprotein incorporation is an essential process in formation of infectious particles of human immunodeficiency virus. Accumulated data have indicated that the cytoplasmic tail of Env gp41 is required for efficient incorporation. By analyzing mutant viruses with truncated cytoplasmic tails, we found that the domain was required in a cell-type-dependent manner for maintaining virus infectivity. Although the viruses with truncated cytoplasmic tails produced from HeLa, A3.01 and SupT1 cells showed a greatly reduced infectivity, those from SW480 and MT-4 cells retained a significant infectivity. To clarify the different effect of the cytoplasmic tail mutation on virus infectivity, we performed biochemical studies on the virions produced from HeLa and SW480 cells. Although the truncation of cytoplasmic tail appeared to reduce the Env incorporation in both cell lines, it caused a significant incorporation of Env precursor with HeLa cells. The results suggested that the cytoplasmic tail regulated selective incorporation of processed Env into virions in a cell-type-dependent manner.