Abstract. Expression of human immunodeficiency virus type 1 (HIV-1) structural proteins requires the presence of the viral trans-activator protein Rev. Rev is localized in the nucleus and binds specifically to the Rev response element (RRE) sequence in viral RNA. Furthermore, the interaction of the Rev activation domain with a cellular cofactor is essential for Rev function in vivo. Using cross-linking experiments and Biospecific Interaction Analysis (BIA) we identify eukaryotic initiation factor 5A (elF-5A) as a cellular factor binding specifically to the HIV-1 Rev activation domain. Indirect immunofluorescence studies demonstrate that a significant fraction of elF-5A localizes to the nucleus. We also provide evidence that Rev transactivation is functionally mediated by elF-5A in Xenopus oocytes. Furthermore, we are able to block Rev function in mammalian cells by antisense inhibition of elF-5A gene expression. Thus, regulation of HIV-1 gene expression by Rev involves the targeting of RREcontaining RNA to components of the cellular translation initiation complex.

Eukaryotic initiation factor 5A(eIF-5A) is a cellular cofactor require d for the function of the human immunodeficiency virus type-1 (HIV-1) Rev trans-activator protein. The majority of a set of eIF-5A mutants did not support growth of yeast cells having an inactivated genomic copy of eIF-5A, indicating that the introduced mutation eliminated eIF-5A activity. Two nonfunctional mutants, eIF-5AM13 and eIF-5AM14, retained their binding capacity for the HIV-1 Rev response element:Rev complex. Both mutants were constitutively expressed in human T cells. When these T cells were infected with replication-competent HIV-1, virus replication was inhibited. The eIF-5AM13 and eIF5AM14 proteins blocked Rev trans-activation and Rev-mediated nuclear export.

(Me-Ile-4)cyclosporin (SDZ NIM 811) is a 4-substituted cyclosporin which is devoid of immunosuppressive activity but retains full capacity for binding to cyclophilin and exhibits potent anti-human immunodeficiency virus type 1 (HIV-1) activity. SDZ NIM 811 selectively inhibits HIV-1 replication in T4 lymphocyte cell lines, in a monocytic cell line, and in HeLa T4 cells. Furthermore, its antiviral activity against laboratory strains and against clinical isolates from geographically distinct regions in primary T4 lymphocytes and in primary monocytes (50%o inhibitory concentration = 0.011 to 0.057 ,g/ml) was demonstrated. SDZ NIM 811 does not inhibit proviral gene expression or virus-specific enzyme functions, either free or bound to cyclophilin. The compound does not influence CD4 expression or inhibit fusion between virus-infected and uninfected cells. SDZ NIM 811 was, however, found to block formation of infectious particles from chronically infected cells. Oral administration to mice, rats, dogs, and monkeys resulted in levels in blood considerably exceeding the drug concentration, which completely blocked virus replication in primary cells. SDZ NIM 811 caused changes of toxicity parameters in rats to a smaller degree than cyclosporine (formerly cyclosporin A). Thus, the potent and selective anti-HIV-1 activity of SDZ NIM 811 and its favorable pharmacokinetic behavior together with its lower nephrotoxicity than that of cyclosporine make this compound a promising candidate for development as an anti-HIV drug.

A library of neomycin B mimetics has been prepared rapidly without chromatography using a neamine-derived aldehyde, tert-butyl isocyanide or isocyanoacetic acid methyl ester, a glycine-conjugated polyethylene glycol (PEG) methyl ether, and various Cbz-N-protected amino acids as substrates in a Ugi-type one-pot reaction. The product linked to PEG was isolated by precipitation in ether. A simultaneous base-catalyzed hydrolysis and de-O-acetylation followed by hydrogenation provided an easy access to a library of neomycin B mimetics, which were screened for binding to the Rev responsive element of HIV mRNA (RRE). Several products were found to be more active than neamine with the IC50 values in the micromolar range.

Various proteins with different biological activities have been observed to be translocated from the nucleus to the cytoplasm in an energy-and signal-dependent manner in eukaryotic cells. This nuclear export is directed by nuclear export signals (NESs), typically characterized by hydrophobic, primarily leucine, amino acid residues. Moreover, it has been shown that CRM1͞exportin 1 is an export receptor for leucine-rich NESs. However, additional NESinteracting proteins have been described. In particular, eukaryotic initiation factor 5A (eIF-5A) has been shown to be a critical cellular cofactor for the nuclear export of the HIV type 1 (HIV-1) Rev trans-activator protein. In this study we compared the nuclear export activity of NESs of different origin. Microinjection of export substrates into the nucleus of somatic cells in combination with specific inhibitors indicated that specific nuclear export pathways exist for different NES-containing proteins. In particular, inhibition of eIF-5A blocked the nuclear export of NESs derived from the HIV-1 Rev and human T cell leukemia virus type I Rex transactivators, whereas nucleocytoplasmic translocation of the protein kinase inhibitor-NES was unaffected. In contrast, however, inhibition of CRM1͞exportin 1 blocked the nuclear export of all NES-containing proteins investigated. Our data confirm that CRM1͞exportin 1 is a general export receptor for leucine-rich NESs and suggest that eIF-5A acts either upstream of CRM1͞exportin 1 or forms a complex with the NES and CRM1͞exportin 1 in the nucleocytoplasmic translocation of the HIV-1 Rev and human T cell leukemia virus type I Rex RNA export factors.In nucleated cells, transport of macromolecules across the nuclear envelope is an active, bidirectional process mediated by the nuclear pore complex (NPC) in a temperature-, energy-, and signal-dependent manner (for reviews, see refs.