Iron(II) supramolecular helicates interfere with the HIV-1 Tat-TAR RNA interaction critical for viral replication (original) (raw)
Related papers
Iron chelators ICL670 and 311 inhibit HIV-1 transcription
Virology, 2007
HIV-1 replication is induced by the excess of iron and iron chelation by desferrioxamine (DFO) inhibits viral replication by reducing proliferation of infected cells. Treatment of the cells with DFO and 2-hydroxy-1-naphthylaldehyde isonicotinoyl hydrazone (311) inhibit expression of proteins that regulate cell-cycle progression, including cycle-dependent kinase 2 (CDK2). Our recent studies showed that CDK2 participates in HIV-1 transcription and viral replication suggesting that inhibition of CDK2 by iron chelators might also affect HIV-1 transcription. Here we evaluated the effect of a clinically approved orally effective iron chelator, 4-[3,5-bis-(hydroxyphenyl) -1,2,4-triazol-1-yl]benzoic acid (ICL670) and 311 on HIV-1 transcription. Both ICL670 and 311 inhibited Tat-induced HIV-1 transcription in CEM-T cells, 293T and HeLa cells. Neither ICL670 nor 311 induced cytotoxicity at concentrations that inhibited HIV-1 transcription. The chelators decreased cellular activity of CDK2 and reduced HIV-1 Tat phosphorylation by CDK2. The ICL670 and 311 did not decrease CDK9 protein level but significantly reduced association of CDK9 with cyclin T1 and reduced phosphorylation of Ser-2 residues of RNA polymerase II C-terminal domain. In conclusion, our findings add to the evidence that iron chelators can inhibit HIV-1 transcription by deregulating inhibiting CDK2 and CDK9. Further consideration should be given to the development of iron chelators for future anti-retroviral therapeutics.
Chemistry & Biology, 2008
The supramolecular iron cylinder, [Fe 2 L 3 ]Cl 4 (L = C 25 H 20 N 4), shows unprecedented DNA binding in vitro, inducing intramolecular DNA coiling and also targeting Y-shaped DNA junctions. We investigated its effects on proliferation and survival in both tumor and normal cell lines. Iron cylinder reduced mitochondrial activity of cultures with potency similar to cisplatin, inhibited the cell cycle, and increased cell death by apoptosis. Associated with this, we observed a lowering of the association of propidium iodide with cellular DNA consistent with an observed competitive displacement of PI from naked DNA by cylinders. Importantly, and in contrast to existing anticancer drugs such as cisplatin, the iron cylinder [Fe 2 L 3 ] 4+ was not genotoxic. In summary, the design of metal complexes such as [Fe 2 L 3 ] 4+ with potential anticancer properties in the absence of genotoxicity may represent a significant step toward therapeutic advancement.
Multivalent binding oligomers inhibit HIV Tat–TAR interaction critical for viral replication
Bioorganic & Medicinal Chemistry Letters, 2009
We describe the development of a new type of scaffold to target RNA structures. Multivalent binding oligomers (MBOs) are molecules in which multiple sidechains extend from a polyamine backbone such that favorable RNA binding occurs. We have used this strategy to develop MBO-based inhibitors to prevent the association of a protein-RNA complex, Tat-TAR, that is essential for HIV replication. In vitro binding assays combined with model cell-based assays demonstrate that the optimal MBOs inhibit Tat-TAR binding at low micromolar concentrations. Antiviral studies are also consistent with the in vitro and cell-based assays. MBOs provide a framework for the development of future RNA-targeting molecules.
Iron Chelator Transmetalative Approach to Inhibit Human Ribonucleotide Reductase
JACS Au
Efforts directed at curtailing the bioavailability of intracellular iron could lead to the development of broad-spectrum anticancer drugs given the metal's role in cancer proliferation and metastasis. Human ribonucleotide reductase (RNR), the key enzyme responsible for synthesizing the building blocks of DNA replication and repair, depends on Fe binding at its R2 subunit to activate the catalytic R1 subunit. This work explores an intracellular iron chelator transmetalative approach to inhibit RNR using the titanium(IV) chemical transferrin mimetic (cTfm) compounds Ti(HBED) and Ti(Deferasirox) 2. Whole-cell EPR studies reveal that the compounds can effectively attenuate RNR activity though seemingly causing different changes to the labile iron pool that may account for differences in their potency against cells. Studies of Ti(IV) interactions with the adenosine nucleotide family at pH 7.4 reveal strong metal binding and extensive phosphate hydrolysis, which suggest the capacity of the metal to disturb the nucleotide substrate pool of the RNR enzyme. By decreasing intracellular Fe bioavailability and altering the nucleotide substrate pool, the Ti cTfm compounds could inhibit the activity of the R1 and R2 subunits of RNR. The compounds arrest the cell cycle in the S phase, indicating suppressed DNA replication, and induce apoptotic cell death. Cotreatment cell viability studies with cisplatin and Ti(Deferasirox) 2 reveal a promising synergism between the compounds that is likely owed to their distinct but complementary effect on DNA replication. KEYWORDS: Titanium(IV) chemical transferrin mimetic complexes, intracellular iron(III) transmetalation, ribonucleotide reductase inhibition, metal-based anticancer strategy, titanium(IV) binding of nucleotides
The bulge region of HIV1 TAR RNA binds metal ions in solution
Nucleic Acids Research, 2002
Binding of Mg 2+ , Ca 2+ and Co(NH 3 ) 6 3+ ions to the HIV-1 TAR RNA in solution was analysed by 19 F NMR spectroscopy, metal ion-induced RNA cleavages and Brownian dynamics (BD) simulations. Chemically synthesised 29mer oligoribonucleotides of the TAR sequence labelled with 5-¯uorouridine (FU) were used for 19 F NMR-monitored metal ion titration. The chemical shift changes of¯uorine resonances FU-23, FU-25 and FU-40 upon titration with Mg 2+ and Ca 2+ ions indicated speci®c, although weak, binding at the bulge region with the dissociation constants (K d ) of 0.9 T 0.6 and 2.7 T 1.7 mM, respectively. Argininamide, inducing largest 19 F chemical shifts changes at FU-23, was used as a reference ligand (K d = 0.3 T 0.1 mM). In the Pb 2+induced TAR RNA cleavage experiment, strong and selective cleavage of the C24-U25 phosphodiester bond was observed, while Mg 2+ and Ca 2+ induced cuts at all 3-nt residues of the bulge. The inhibition of Pb 2+ -speci®c TAR cleavage by di-and trivalent metal ions revealed a binding speci®city [in the order Co(NH 3 ) 6 3+ > Mg 2+ > Ca 2+ ] at the bulge site. A BD simulation search of potential magnesium ion sites within the NMR structure of HIV-1 TAR RNA was conducted on a set of 20 conformers (PDB code 1ANR). For most cases, the bulge region was targeted by magnesium cations.
Anti-HIV effect of iron chelators: different mechanisms involved
Journal of Clinical Virology, 2001
Background: Drugs for the treatment of AIDS have been directed to specific events in the human immunodeficiency virus (HIV-1) life cycle, aimed to stop viral replication by inhibition of reverse transcriptase or protease activity. Studies showing that oxidative stress and iron may be important in the activation of HIV-1 have focused attention on the potential therapeutic use of iron chelators. Objecti6es: The goal of this review is to describe several possibilities as to how iron is involved in the replication of HIV and how iron chelation may interfere in this process. Study design: First some physico-chemical properties of iron concerning solubility, oxidation -reduction potential, catalysis, and chelation will be discussed. In the second part, the role of iron in various biochemical systems is explained. Results: Nuclear factor kappa B (NF-kB) activation, regulating proviral transcription, can be influenced by iron through the production of reactive oxygen species. A second route by which iron chelation could influence HIV replication, is by inhibition of DNA synthesis through inactivation of iron-dependent ribonucleotide reductase. Another strategy which can be employed in targeting iron chelators against HIV-1, is direct oxidative viral RNA/DNA attack. This could be achieved by bleomycin, a cytostatic agent with the ability to form a complex with DNA and RNA. Conclusion: Chelation may withhold iron from viral metabolism but on the other hand may also favor catalysis of reactive oxygen species directed to viral constituents. In combination with existing antivirals, iron chelation could add to improve the treatment of HIV-disease.
Towards an Improved anti-HIV Activity of NRTI via Metal-Organic Frameworks Nanoparticles
Advanced Healthcare Materials, 2013
Nanoscale mesoporous iron carboxylates metal-organic frameworks (nano-MOFs) have recently emerged as promising platforms for drug delivery, showing biodegradability, biocompatibility and important loading capability of challenging highly water-soluble drugs such as azidothymidine tryphosphate (AZT-TP). In this study, nanoMOFs made of iron trimesate (MIL-100) were able to act as effi cient molecular sponges, quickly adsorbing up to 24 wt% AZT-TP with entrapment effi ciencies close to 100%, without perturbation of the supramolecular crystalline organization. These data are in agreement with molecular modelling predictions, indicating maximal loadings of 33 wt% and preferential location of the drug in the large cages. Spectrophotometry, isothermal titration calorimetry and solid state NMR investigations enabled to gain insight on the mechanism of interaction of AZT and AZT-TP with the nanoMOFs, pointing out the crucial role of phosphates strongly coordinating with the unsaturated iron(III) sites. Finally, contrarily to the free AZT-TP, the loaded nanoparticles effi ciently penetrate and release their cargo of active triphosphorylated AZT inside major HIV target cells, effi ciently protecting against HIV infection.
An Inhibitor of the Tat/TAR RNA Interaction that Effectively Suppresses HIV1 Replication
Proceedings of The National Academy of Sciences, 1997
One of the first steps in HIV gene expression is the recruitment of Tat protein to the transcription machinery after its binding to the RNA response element TAR. Starting from a pool of 3.2 ؋ 10 6 individual chemical entities, we were able to select a hybrid peptoid͞peptide oligomer of 9 residues (CGP64222) that was able to block the formation of the Tat͞TAR RNA complex in vitro at nanomolar concentrations. NMR studies demonstrated that the compound binds similarly to polypeptides derived from the Tat protein and induces a conformational change in TAR RNA at the Tatbinding site. In addition, 10-30 M CGP64222 specifically inhibited Tat activity in a cellular Tat-dependent transactivation assay [fusion-induced gene stimulation (FIGS) assay] and blocked HIV-1 replication in primary human lymphocytes. By contrast, peptides of a comparable size and side-chain composition inhibited cell fusion in the FIGS assay and only partially inhibited HIV-1 replication in primary human lymphocytes. Thus, we have discovered a compound, CGP64222, that specifically inhibits the Tat͞TAR RNA interaction, both in vitro and in vivo.
Antimicrobial agents and chemotherapy, 2014
HIV-1 transcription is activated by the Tat protein, which recruits CDK9/cyclin T1 to the HIV-1 promoter. CDK9 is phosphorylated by CDK2, which facilitates formation of the high-molecular-weight positive transcription elongation factor b (P-TEFb) complex. We previously showed that chelation of intracellular iron inhibits CDK2 and CDK9 activities and suppresses HIV-1 transcription, but the mechanism of the inhibition was not understood. In the present study, we tested a set of novel iron chelators for the ability to inhibit HIV-1 transcription and elucidated their mechanism of action. Novel phenyl-1-pyridin-2yl-ethanone (PPY)-based iron chelators were synthesized and examined for their effects on cellular iron, HIV-1 inhibition, and cytotoxicity. Activities of CDK2 and CDK9, expression of CDK9-dependent and CDK2-inhibitory mRNAs, NF-κB expression, and HIV-1- and NF-κB-dependent transcription were determined. PPY-based iron chelators significantly inhibited HIV-1, with minimal cytotox...