BSG and viral infectious disease: For example, the interaction between CYPA and HIV Gag was proposed to facilitate disassembly of the viral RNA containing core following virus entry and thus supports the efficient reverse transcription of the HIV-1 genome (Luban et al., 1993; Ott, 2002) CYPA also enhances virus attachment to the host cell membrane through interactions with heparans (Saphire et al., 2000) and after membrane fusion through interaction with CD147, thereby promoting viral infection.