ERVW-1 and HIV-1 infection: Here, we examine in depth the role of MARCH2 during Human Immunodeficiency Virus type 1 (HIV-1) infection and show that it utilizes two mechanisms to inhibit HIV-1: 1) prevents the envelope glycoprotein incorporation into nascent virions in a RING-CH-dependent manner, 2) when incorporated in virions, it blocks virus-cell membrane fusion in a RING-CH independent manner.