Analysis and Localization of Cyclophilin A Found in the Virions of Human Immunodeficiency Virus Type 1 MN Strain

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Abstract
Previous reports have shown that cyclophilin A (CyPA) is found to be specifically associated with human immunodeficiency virus type-1 (HIV-1) virions and is required for infectivity (Franke et al. Nature 372:359; Thali et al. Nature 372:363). We have examined CyPA associated with HIV-1MN virions. Virions from infected human lymphoid cells were analyzed by high-pressure liquid chromatography (HPLC), protein sequence, and immunoblot analysis. At least three forms of CyPA were found: an unmodified form, an N-terminally modified form, and an N-terminally modified form that migrates as a larger isoform on a reducing-SDS polyacrylamide gel. Using a protease digestion procedure, CyPA that is associated with virions was found to be located inside the viral membrane. Similar examination of SIVMne. produced by HUT-78 human T cells did not detect specific incorporation of CyPA into SIV virions. Our results are consistent with the role of CyPA acting early in the infectious process of HIV-1.