Heat-shock protein 70 can replace viral protein R of HIV-1 during nuclear import of the viral preintegration complex

Heat-shock proteins (Hsp's) are a family of molecular chaperones that contr ibute to protection from environmental stress. In this report, we demonstra te that a member of this family, Hsp70, facilitates nuclear import of HIV-1 preintegration complexes (PICs). The mechanism of this activity appears to be similar to the one used by Vpr, an HIV-1 protein regulating viral nucle ar import and replication in macrophages. Indeed Hsp70 stimulated binding o f HIV-1 matrix antigen to GST-karyopherin alpha fusion protein and rescued nuclear import of a Vpr-defective HIV-1 strain in vitro. Binding studies wi th truncated forms of GST-karyopherin alpha demonstrated that both Vpr and Hsp70 bind to a region in the amino-terminal part of the karyopherin alpha molecule. This region appears to be distinct from the binding sites for two other karyopherin alpha cargoes, basic-type NLS-containing proteins and tr anscription factor STAT-1. Vpr competed with Hsp70 for binding to karyopher in alpha. These results suggest the presence of a novel regulatory site on karyopherin cu which is used by Hsp70 and Vpr to stimulate interaction betw een the HIV-1 PIC and karyopherin alpha and thus promote viral nuclear impo rt, (C) 2000 Academic Press.