title: Inhibition of both HIV-1 reverse transcription and gene expression by a cyclic peptide that binds the Tat-transactivating response element (TAR) RNA.
abstract: The RNA response element TAR plays a critical role in HIV replication by providing a binding site for the recruitment of the viral transactivator protein Tat. Using a structure-guided approach, we have developed a series of conformationally-constrained cyclic peptides that act as structural mimics of the Tat RNA binding region and block Tat-TAR interactions at nanomolar concentrations in vitro. Here we show that these compounds block Tat-dependent transcription in cell-free systems and in cell-based reporter assays. The compounds are also cell permeable, have low toxicity, and inhibit replication of diverse HIV-1 strains, including both CXCR4-tropic and CCR5-tropic primary HIV-1 isolates of the divergent subtypes A, B, C, D and CRF01_AE. In human peripheral blood mononuclear cells, the cyclic peptidomimetic L50 exhibited an IC(50) ∼250 nM. Surprisingly, inhibition of LTR-driven HIV-1 transcription could not account for the full antiviral activity. Timed drug-addition experiments revealed that L-50 has a bi-phasic inhibition curve with the first phase occurring after HIV-1 entry into the host cell and during the initiation of HIV-1 reverse transcription. The second phase coincides with inhibition of HIV-1 transcription. Reconstituted reverse transcription assays confirm that HIV-1 (-) strand strong stop DNA synthesis is blocked by L50-TAR RNA interactions in-vitro. These findings are consistent with genetic evidence that TAR plays critical roles both during reverse transcription and during HIV gene expression. Our results suggest that antiviral drugs targeting TAR RNA might be highly effective due to a dual inhibitory mechanism.
authors.affiliation: Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, United States of America.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Lalonde
authors.forename: Michael A
authors.initials: MA
authors.lastname: Lobritz
authors.forename: Annette
authors.initials: A
authors.lastname: Ratcliff
authors.forename: Mastooreh
authors.initials: M
authors.lastname: Chamanian
authors.forename: Zafiria
authors.initials: Z
authors.lastname: Athanassiou
authors.forename: Mudit
authors.initials: M
authors.lastname: Tyagi
authors.forename: Julian
authors.initials: J
authors.lastname: Wong
authors.forename: John A
authors.initials: JA
authors.lastname: Robinson
authors.forename: Jonathan
authors.initials: J
authors.lastname: Karn
authors.forename: Gabriele
authors.initials: G
authors.lastname: Varani
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Arts
mesh_terms: D000595:Amino Acid Sequence; D019380:Anti-HIV Agents / Q000494:pharmacology*; D001665:Binding Sites / Q000187:drug effects; D045744:Cell Line, Tumor; D015870:Gene Expression; D015967:Gene Expression Regulation, Viral; D016325:HIV Long Terminal Repeat / Q000187:drug effects*; D054303:HIV Reverse Transcriptase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D015497:HIV-1 / Q000187:drug effects* / Q000235:genetics / Q000502:physiology; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000821:virology; D010456:Peptides, Cyclic / Q000378:metabolism / Q000494:pharmacology*; D012367:RNA, Viral / Q000235:genetics; D048348:Reverse Transcription / Q000187:drug effects*; D015533:Transcriptional Activation / Q000187:drug effects; D014779:Virus Replication / Q000187:drug effects; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D019380:Anti-HIV Agents; D010456:Peptides, Cyclic; D012367:RNA, Viral; D054322:tat Gene Products, Human Immunodeficiency Virus; C514824:reverse transcriptase, Human immunodeficiency virus 1; D054303:HIV Reverse Transcriptase