HIV-1 Rev 34-50

Formation of a macromolecular complex between the RNA binding protein HIV-1 Rev and HIV-1 mRNA is an essential prerequisite for nuclear export and subsequent expression of HIV-1 mRNA. The arginine rich peptide TRQARRNRRRRWRARQR, corresponding to residues 34-50 of HIV-1 Rev, contains the mRNA binding motif. We prepared a thioether linked Rev34-50-cellulose conjugate to affinity purify a fragment of synthetic mRNA corresponding to the high affinity binding site for Rev. The correctly folded fraction of mRNA (27.5%) was isolated from a crude synthetic mixture.

Rev is an essential HIV-1 regulatory protein that binds the Rev responsive element (RRE) within the env gene of the HIV-1 RNA genome and is involved in transport of unspliced or partially spliced viral mRNA from the cell nucleus to the cytoplasm. Previous studies have shown that a short alpha-helical peptide derived from Rev (Rev 34-50), and a truncated form of the RRE sequence provide a useful in vitro system to study this interaction while still preserving the essential aspects of the native complex. We have selectively incorporated the fluorescent probe 2-aminopurine 2'-O-methylriboside (2-AP) into the RRE sequence in nonperturbing positions (A68 and U72) such that the binding of both Rev peptide and aminoglycoside ligands could be characterized directly by fluorescence methods. Rev peptide binding to the RRE-72AP variant resulted in a 2-fold fluorescence increase that provided a useful signal to monitor this binding interaction (K(D) = 20 +/- 7 nM). Using stopped-flow kinetic measurements, we have shown that specific Rev peptide binding occurs by a two-step process involving diffusion-controlled encounter, followed by isomerization of the RNA. Using the RRE-68AP and -72AP constructs, three classes of binding sites for the aminoglycoside neomycin were unambiguously detected. The first site is noninhibitory to Rev binding (K(D) = 0.24 +/- 0.040 microM), the second site inhibited Rev binding in a competitive fashion (K(D) = 1. 8 +/- 0.8 microM), and the third much weaker site (or sites) is attributed to nonspecific binding (K(D) >/= 40 microM). Complementary NMR measurements have shown that neomycin forms both a specific binary complex with RRE and a specific ternary complex with RRE and Rev. NMR data further suggest that neomycin occupies a similar high-affinity binding site in both the binary and ternary complexes, and that this site is located in the lower stem region of RRE.

Rev, a viral regulatory protein of HIV-1, binds through its arginine-rich domain to the Rev-responsive element (RRE), a secondary structure in transcribed HIV-1 RNA. Binding of Rev to RRE mediates export of singly spliced or unspliced mRNAs from the nucleus to the cytoplasm. It has been previously shown that a certain arginine-rich peptide exhibits not only RRE-binding ability but also cell permeability and antagonism of CXCR4, one of the major coreceptors of HIV-1. Here we designed and synthesized arginine-rich peptides derived from the RNA-binding domain of Rev (Rev(34-50)) and evaluated their anti-HIV-1 activities. Rev(34-50)-A(4)C, comprising Rev(34-50) with AAAAC at the C-terminus to increase the alpha-helicity, inhibited HIV-1 entry by CXCR4 antagonism and virus production in persistently HIV-1-infected PM1-CCR5 cells. Interestingly, similar motif of human lymphotropic virus type I Rex (Rex(1-21)) also exerted moderate anti-HIV-1 activity. These results indicate that arginine-rich peptide, Rev(34-50)-A(4)C exerts dual antagonism against CXCR4 and Rev.