Reverse Transcription of Human Immunodeficiency Virus Type 1 is Blocked by Retroviral Zinc Finger Inhibitors

The Cys-Xaa₂-Cys-Xaa₄-His-Xaa₄-Cys zinc fingers of retroviral nucleocapsid (NC) proteins are prime antiviral targets due to conservation of the Cys and His chelating residues and the absolute requirement of these fingers in both early and late phases of retroviral replication. Certain 2,2′-dithiobisbenzamides (DIBAs) chemically modify the Cys residues of the fingers, thereby inhibiting in vitro replication of human immunodeficiency virus type 1 (HIV-1). We examined the consequences of DIBA interaction with cell-free virions and their subsequent ability to initiate new rounds of infection. The DIBAs entered intact virions and chemically modified the p7NC proteins, resulting in extensive disulphide cross-linkage among zinc fingers of adjacent p7NC molecules. Likewise, treatment of Pr55^gag-laden pseudovirions, used as a model of virion particles, with DIBAs resulted in Pr55^gag cross-linkage. In contrast, monomeric p7NC protein did not form cross-linkages after DIBA treatment, indicating that the retroviral zinc finger proteins must exist in close proximity for cross-linkage to occur. Cross-linkage of p7NC in virions correlated with loss of infectivity and decreased proviral DNA synthesis during acute infection, even though DIBAs did not inhibit virus attachment to host cells or reverse transcriptase enzymatic activity. Thus, DIBA-type molecules impair the ability of HIV-1 virions to initiate reverse transcription through their action on the retroviral zinc finger, thereby blocking further rounds of replication.