51
|
Kellish PC, Kumar S, Mack TS, Spano MN, Hennig M, Arya DP. Multivalent Amino Sugars to Recognize Different TAR RNA Conformations. MEDCHEMCOMM 2014; 5:1235-1246. [PMID: 27076899 PMCID: PMC4828046 DOI: 10.1039/c4md00165f] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Neomycin dimers synthesized using "click chemistry" with varying functionality and length in the linker region have been shown to be effective in targeting the HIV-1 TAR RNA region of the HIV virus. TAR (Transactivation Response) RNA region, a 59 base pair stem loop structure located at the 5'-end of all nascent viral transcripts interacts with its target, a key regulatory protein, Tat, and necessitates the replication of HIV-1 virus. Ethidium bromide displacement and FRET competition assays have revealed nanomolar binding affinity between neomycin dimers and wildtype TAR RNA while in case of neomycin, only a weak binding was detected. Here, NMR and FID-based comparisons reveal an extended binding interface for neomycin dimers involving the upper stem of the TAR RNA thereby offering an explanation for increased affinities. To further explore the potential of these modified aminosugars we have extended binding studies to include four TAR RNA mutants that display conformational differences with minimal sequence variation. The differences in binding between neomycin and neomycin dimers is characterized with TAR RNA mutants that include mutations to the bulge region, hairpin region, and both the bulge and hairpin regions. Our results demonstrate the effect of these mutations on neomycin binding and our results show that linker functionalities between dimeric units of neomycin can distinguish between the conformational differences of mutant TAR RNA structures.
Collapse
Affiliation(s)
- Patrick C. Kellish
- Laboratory of Medicinal Chemistry, Department of Chemistry, Clemson University, Clemson, South Carolina 29634, United States
| | - Sunil Kumar
- Laboratory of Medicinal Chemistry, Department of Chemistry, Clemson University, Clemson, South Carolina 29634, United States
| | - Todd S. Mack
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, 70 President St., Charleston, SC 29425
| | | | - Mirko Hennig
- Department of Biochemistry and Molecular Biology, Medical University of South Carolina, 70 President St., Charleston, SC 29425
| | - Dev P. Arya
- Laboratory of Medicinal Chemistry, Department of Chemistry, Clemson University, Clemson, South Carolina 29634, United States
- NUBAD, LLC, 900B West Faris Rd., Greenville, SC 29605
| |
Collapse
|
52
|
Abstract
Using on- and off-resonance carbon and nitrogen R1ρ NMR relaxation dispersion in concert with mutagenesis and NMR chemical shift fingerprinting, we show that the transactivation response element RNA from the HIV-1 exists in dynamic equilibrium with a transient state that has a lifetime of ∼2 ms and population of ∼0.4%, which simultaneously remodels the structure of a bulge, stem, and apical loop. This is accomplished by a global change in strand register, in which bulge residues pair up with residues in the upper stem, causing a reshuffling of base pairs that propagates to the tip of apical loop, resulting in the creation of three noncanonical base pairs. Our results show that transient states can remodel distant RNA motifs and possibly give rise to mechanisms for rapid long-range communication in RNA that can be harnessed in processes such as cooperative folding and ribonucleoprotein assembly.
Collapse
|
53
|
Mustoe AM, Al-Hashimi HM, Brooks CL. Coarse grained models reveal essential contributions of topological constraints to the conformational free energy of RNA bulges. J Phys Chem B 2014; 118:2615-27. [PMID: 24547945 PMCID: PMC3983386 DOI: 10.1021/jp411478x] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
![]()
Recent studies have shown that simple
stereochemical constraints
encoded at the RNA secondary structure level significantly restrict
the orientation of RNA helices across two-way junctions and yield
physically reasonable distributions of RNA 3D conformations. Here
we develop a new coarse-grain model, TOPRNA, that is optimized for
exploring detailed aspects of these topological constraints in complex
RNA systems. Unlike prior models, TOPRNA effectively treats RNAs as
collections of semirigid helices linked by freely rotatable single
strands, allowing us to isolate the effects of secondary structure
connectivity and sterics on 3D structure. Simulations of bulge junctions
show that TOPRNA captures new aspects of topological constraints,
including variations arising from deviations in local A-form structure,
translational displacements of the helices, and stereochemical constraints
imposed by bulge-linker nucleotides. Notably, these aspects of topological
constraints define free energy landscapes that coincide with the distribution
of bulge conformations in the PDB. Our simulations also quantitatively
reproduce NMR RDC measurements made on HIV-1 TAR at low salt concentrations,
although not for different TAR mutants or at high salt concentrations.
Our results confirm that topological constraints are an important
determinant of bulge conformation and dynamics and demonstrate the
utility of TOPRNA for studying the topological constraints of complex
RNAs.
Collapse
Affiliation(s)
- Anthony M Mustoe
- Departments of Biophysics and ‡Chemistry, University of Michigan , 930 North University Avenue, Ann Arbor, Michigan 48109, United States
| | | | | |
Collapse
|
54
|
Borkar AN, De Simone A, Montalvao RW, Vendruscolo M. A method of determining RNA conformational ensembles using structure-based calculations of residual dipolar couplings. J Chem Phys 2014; 138:215103. [PMID: 23758399 DOI: 10.1063/1.4804301] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
We describe a method of determining the conformational fluctuations of RNA based on the incorporation of nuclear magnetic resonance (NMR) residual dipolar couplings (RDCs) as replica-averaged structural restraints in molecular dynamics simulations. In this approach, the alignment tensor required to calculate the RDCs corresponding to a given conformation is estimated from its shape, and multiple replicas of the RNA molecule are simulated simultaneously to reproduce in silico the ensemble-averaging procedure performed in the NMR measurements. We provide initial evidence that with this approach it is possible to determine accurately structural ensembles representing the conformational fluctuations of RNA by applying the reference ensemble test to the trans-activation response element of the human immunodeficiency virus type 1.
Collapse
Affiliation(s)
- Aditi N Borkar
- Department of Chemistry, University of Cambridge, Cambridge, United Kingdom
| | | | | | | |
Collapse
|
55
|
Al-Hashimi HM. NMR studies of nucleic acid dynamics. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 237:191-204. [PMID: 24149218 PMCID: PMC3984477 DOI: 10.1016/j.jmr.2013.08.014] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/02/2013] [Accepted: 08/23/2013] [Indexed: 05/12/2023]
Abstract
Nucleic acid structures have to satisfy two diametrically opposite requirements; on one hand they have to adopt well-defined 3D structures that can be specifically recognized by proteins; on the other hand, their structures must be sufficiently flexible to undergo very large conformational changes that are required during key biochemical processes, including replication, transcription, and translation. How do nucleic acids introduce flexibility into their 3D structure without losing biological specificity? Here, I describe the development and application of NMR spectroscopic techniques in my laboratory for characterizing the dynamic properties of nucleic acids that tightly integrate a broad set of NMR measurements, including residual dipolar couplings, spin relaxation, and relaxation dispersion with sample engineering and computational approaches. This approach allowed us to obtain fundamental new insights into directional flexibility in nucleic acids that enable their structures to change in a very specific functional manner.
Collapse
Affiliation(s)
- Hashim M Al-Hashimi
- Department of Chemistry & Biophysics, University of Michigan, 930 North University Avenue, Ann Arbor, MI 48109-1055, USA.
| |
Collapse
|
56
|
Pascale L, Azoulay S, Di Giorgio A, Zenacker L, Gaysinski M, Clayette P, Patino N. Thermodynamic studies of a series of homologous HIV-1 TAR RNA ligands reveal that loose binders are stronger Tat competitors than tight ones. Nucleic Acids Res 2013; 41:5851-63. [PMID: 23605042 PMCID: PMC3675469 DOI: 10.1093/nar/gkt237] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
RNA is a major drug target, but the design of small molecules that modulate RNA function remains a great challenge. In this context, a series of structurally homologous 'polyamide amino acids' (PAA) was studied as HIV-1 trans-activating response (TAR) RNA ligands. An extensive thermodynamic study revealed the occurence of an enthalpy-entropy compensation phenomenon resulting in very close TAR affinities for all PAA. However, their binding modes and their ability to compete with the Tat fragment strongly differ according to their structure. Surprisingly, PAA that form loose complexes with TAR were shown to be stronger Tat competitors than those forming tight ones, and thermal denaturation studies demonstrated that loose complexes are more stable than tight ones. This could be correlated to the fact that loose and tight ligands induce distinct RNA conformational changes as revealed by circular dichroism experiments, although nuclear magnetic resonance (NMR) experiments showed that the TAR binding site is the same in all cases. Finally, some loose PAA also display promising inhibitory activities on HIV-infected cells. Altogether, these results lead to a better understanding of RNA interaction modes that could be very useful for devising new ligands of relevant RNA targets.
Collapse
Affiliation(s)
- Lise Pascale
- Institut de Chimie de Nice UMR7272, Université de Nice Sophia Antipolis, 06108 Nice Cedex, France
| | | | | | | | | | | | | |
Collapse
|
57
|
Jia X, Zhang J, Sun W, He W, Jiang H, Chen D, Murchie AIH. Riboswitch control of aminoglycoside antibiotic resistance. Cell 2013; 152:68-81. [PMID: 23332747 DOI: 10.1016/j.cell.2012.12.019] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2012] [Revised: 06/04/2012] [Accepted: 12/13/2012] [Indexed: 12/23/2022]
Abstract
The majority of riboswitches are regulatory RNAs that regulate gene expression by binding small-molecule metabolites. Here we report the discovery of an aminoglycoside-binding riboswitch that is widely distributed among antibiotic-resistant bacterial pathogens. This riboswitch is present in the leader RNA of the resistance genes that encode the aminoglycoside acetyl transferase (AAC) and aminoglycoside adenyl transferase (AAD) enzymes that confer resistance to aminoglycoside antibiotics through modification of the drugs. We show that expression of the AAC and AAD resistance genes is regulated by aminoglycoside binding to a secondary structure in their 5' leader RNA. Reporter gene expression, direct measurements of drug RNA binding, chemical probing, and UV crosslinking combined with mutational analysis demonstrate that the leader RNA functions as an aminoglycoside-sensing riboswitch in which drug binding to the leader RNA leads to the induction of aminoglycosides antibiotic resistance.
Collapse
Affiliation(s)
- Xu Jia
- Key Laboratory of Molecular Medicine, the Ministry of Education, Department of Biochemistry and Molecular Biology, Fudan University Shanghai Medical College, Shanghai 200032, China
| | | | | | | | | | | | | |
Collapse
|
58
|
Divya PS, Jain K, Sobhia ME. From peptides to peptidomimetics: rational design of potential PKC-β II inhibitors. Med Chem Res 2013. [DOI: 10.1007/s00044-012-0056-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
|
59
|
Li CH, Zuo ZC, Su JG, Xu XJ, Wang CX. The interactions and recognition of cyclic peptide mimetics of Tat with HIV-1 TAR RNA: a molecular dynamics simulation study. J Biomol Struct Dyn 2012; 31:276-87. [PMID: 22943434 DOI: 10.1080/07391102.2012.698248] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The interaction of HIV-1 trans-activator protein Tat with its cognate trans-activation response element (TAR) RNA is critical for viral transcription and replication. Therefore, it has long been considered as an attractive target for the development of antiviral compounds. Recently, the conformationally constrained cyclic peptide mimetics of Tat have been tested to be a promising family of lead peptides. Here, we focused on two representative cyclic peptides termed as L-22 and KP-Z-41, both of which exhibit excellent inhibitory potency against Tat and TAR interaction. By means of molecular dynamics simulations, we obtained a detailed picture of the interactions between them and HIV-1 TAR RNA. In results, it is found that the binding modes of the two cyclic peptides to TAR RNA are almost identical at or near the bulge regions, whereas the binding interfaces at the apical loop exhibit large conformational heterogeneity. In addition, it is revealed that electrostatic interaction energy contributes much more to KP-Z-41 complex formation than to L-22 complex, which is the main source of energy that results in a higher binding affinity of KP-Z-41 over-22 for TAR RNA. Furthermore, we identified a conserved motif RRK (Arg-Arg-Lys) that is shown to be essential for specific binding of this class of cyclic peptides to TAR RNA. This work can provide a useful insight into the design and modification of cyclic peptide inhibitors targeting the association of HIV-1 Tat and TAR RNA.
Collapse
Affiliation(s)
- Chun Hua Li
- College of Life Science and Bioengineering, Beijing University of Technology, Pingleyuan 100, Chaoyang District, Beijing 100124, China.
| | | | | | | | | |
Collapse
|
60
|
|
61
|
Nafisi S, Manouchehri F, Bonsaii M. Study on the interaction of glycyrrhizin and glycyrrhetinic acid with RNA. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2012; 111:27-34. [PMID: 22513095 DOI: 10.1016/j.jphotobiol.2012.03.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2012] [Revised: 03/05/2012] [Accepted: 03/13/2012] [Indexed: 11/17/2022]
Abstract
Glycyrrhizin is a well known pharmacologically bioactive natural glycoside. Glycyrrhizin (GL) has been widely used as a therapeutic agent for chronic active liver diseases. Glycyrrhetinic acid is an aglycone and an active metabolite of glycyrrhizin. This study is the first attempt to locate the binding sites of glycyrrhizin and glycyrrhetinic acid to RNA. The effect of the ligand complexation on RNA aggregation was investigated in aqueous solution at physiological conditions, using constant RNA concentration (6.25 mM) and various ligand/polynucleotide (phosphate) ratios of 1/280, 1/240, 1/120, 1/80, 1/40, 1/20, 1/10, 1/5, 1/2 and 1/1. Fourier transform infrared (FTIR) and UV-Visible spectroscopic methods as well as molecular modeling were used to determine the ligand binding modes, the binding constants, and the stability of ligands-RNA complexes in aqueous solution. Spectroscopic evidence showed that glycyrrhizin and glycyrrhetinic acid bind RNA via G-C and A-U base pairs as well as the backbone phosphate group with overall binding constants of K(GL-RNA)=3.03×10(3)M(-1), K(GA-RNA)=2.71×10(3)M(-1). The affinity of ligands-RNA binding is in the order of glycyrrhizin>glycyrrhetinic acid. RNA remains in the A-family structure, while biopolymer aggregation occurred at high triterpenoid concentrations.
Collapse
Affiliation(s)
- Shohreh Nafisi
- Department of Chemistry, Islamic Azad University, Central Tehran Branch (IAUCTB), Tehran, Iran.
| | | | | |
Collapse
|
62
|
Bryson DI, Zhang W, McLendon PM, Reineke TM, Santos WL. Toward targeting RNA structure: branched peptides as cell-permeable ligands to TAR RNA. ACS Chem Biol 2012; 7:210-7. [PMID: 22003984 DOI: 10.1021/cb200181v] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Rational design of RNA ligands continues to be a formidable challenge, but the potential powerful applications in biology and medicine catapults it to the forefront of chemical research. Indeed, small molecule and macromolecular intervention are attractive approaches, but selectivity and cell permeability can be a hurdle. An alternative strategy is to use molecules of intermediate molecular weight that possess large enough surface area to maximize interaction with the RNA structure but are small enough to be cell-permeable. Herein, we report the discovery of nontoxic and cell-permeable branched peptide (BP) ligands that bind to TAR RNA in the low micromolar range from on-bead high-throughput screening of 4,096 compounds. TAR is a short RNA motif in the 5'-UTR of HIV-1 that is responsible for efficient generation of full RNA transcripts. We demonstrate that BPs are selective for the native TAR RNA structure and that "branching" in peptides provides multivalent interaction, which increases binding affinity to RNA.
Collapse
Affiliation(s)
- David I. Bryson
- Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Wenyu Zhang
- Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Patrick M. McLendon
- Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Theresa M. Reineke
- Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
| | - Webster L. Santos
- Department of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
| |
Collapse
|
63
|
Huang W, Varani G, Drobny GP. Interactions of protein side chains with RNA defined with REDOR solid state NMR. JOURNAL OF BIOMOLECULAR NMR 2011; 51:347-356. [PMID: 21947838 DOI: 10.1007/s10858-011-9573-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2011] [Accepted: 08/11/2011] [Indexed: 05/31/2023]
Abstract
Formation of the complex between human immunodeficiency virus type-1 Tat protein and the transactivation response region (TAR) RNA is vital for transcriptional elongation, yet the structure of the Tat-TAR complex remains to be established. The NMR structures of free TAR, and TAR bound to Tat-derived peptides have been obtained by solution NMR, but only a small number of intermolecular NOEs could be identified unambiguously, preventing the determination of a complete structure. Here we show that a combination of multiple solid state NMR REDOR experiments can be used to obtain multiple distance constraints from (15)N to (13)C spins within the backbone and side chain guanidinium groups of arginine in a Tat-derived peptide, using (19)F spins incorporated into the base of U23 in TAR and (31)P spins in the P22 and P23 phosphate groups. Distances between the side chain of Arg52 and the base and phosphodiester backbone near U23 measured by REDOR NMR are comparable to distances observed in solution NMR-derived structural models, indicating that interactions of TAR RNA with key amino acid side chains in Tat are the same in the amorphous solid state as in solution. This method is generally applicable to other protein-RNA complexes where crystallization or solution NMR has failed to provide high resolution structural information.
Collapse
Affiliation(s)
- Wei Huang
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington, DC 98195, USA
| | | | | |
Collapse
|
64
|
Smith AL, Kassman J, Srour KJ, Soto AM. Effect of salt concentration on the conformation of TAR RNA and its association with aminoglycoside antibiotics. Biochemistry 2011; 50:9434-45. [PMID: 21916409 DOI: 10.1021/bi200835t] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
RNA is an important biological target because it plays essential roles in many pathogenic and normal cellular processes. The design of inhibitors that target RNA involves optimization of noncovalent interactions, including van der Waals, hydrogen bond, and electrostatic interactions. Although sometimes regarded as nonspecific, electrostatic interactions are important in this optimization because the specific position of the phosphates may allow for specific charge-charge interactions with bound ligands. In this work, we have investigated the contribution of electrostatic interactions to the binding affinity of aminoglycoside antibiotics for TAR RNA. Because the charges in aminoglycoside antibiotics are provided by protonated amino groups, it is difficult to separate the contribution of hydrogen bonds and electrostatics to their binding specificity. Hence, we have investigated the dependence of the binding affinity on salt concentration, which should affect only the electrostatic contributions. Our results show that four aminoglycoside antibiotics (paromomycin, kanamycin-B, gentamycin, and tobramycin) bind TAR RNA with different affinities. Furthermore, the dependence of the binding affinity on salt concentration is different for kanamycin-B and paromomycin, with kanamycin-B showing a stronger dependence. Because all these antibiotics contain five positive charges, the results suggest that each antibiotic orients its charges in different ways when bound to TAR RNA. Our overall results support the idea that charge-charge interactions can contribute significantly to the specific binding of antibiotics to TAR RNA. Hence, the exact position of the charges should be considered in the design of any inhibitor of the interactions of TAR RNA.
Collapse
Affiliation(s)
- Amy L Smith
- Department of Chemistry, Towson University, Towson, Maryland 21252, United States
| | | | | | | |
Collapse
|
65
|
A small-molecule probe induces a conformation in HIV TAR RNA capable of binding drug-like fragments. J Mol Biol 2011; 410:984-96. [PMID: 21763501 DOI: 10.1016/j.jmb.2011.03.039] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2011] [Revised: 03/15/2011] [Accepted: 03/17/2011] [Indexed: 12/29/2022]
Abstract
The HIV-1 transactivation response (TAR) element-Tat interaction is a potentially valuable target for treating HIV infection, but efforts to develop TAR-binding antiviral drugs have not yet yielded a successful candidate for clinical development. In this work, we describe a novel approach toward screening fragments against RNA that uses a chemical probe to target the Tat-binding region of TAR. This probe fulfills two critical roles in the screen: by locking the RNA into a conformation capable of binding other fragments, it simultaneously allows the identification of proximal binding fragments by ligand-based NMR. Using this approach, we have discovered six novel TAR-binding fragments, three of which were docked relative to the probe-RNA structure using experimental NMR restraints. The consistent orientations of functional groups in our data-driven docked structures and common electrostatic properties across all fragment leads reveal a surprising level of selectivity by our fragment-sized screening hits. These models further suggest linking strategies for the development of higher-affinity lead compounds for the inhibition of the TAR-Tat interaction.
Collapse
|
66
|
Niu Y, Jones AJ, Wu H, Varani G, Cai J. γ-AApeptides bind to RNA by mimicking RNA-binding proteins. Org Biomol Chem 2011; 9:6604-9. [PMID: 21826330 DOI: 10.1039/c1ob05738c] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The interactions between proteins and RNAs are of vital importance for many cellular processes, including transcription and processing of RNA, translation, and viral infections. Here we report an γ-AApeptide that can mimic HIV-1 Tat protein and bind to TAR RNAs of HIV and BIV with nanomolar affinity, comparable to that of the RNA-binding fragment of Tat (amino acids 49-58). The interaction is resistant to the presence of a large excess of tRNA. With resistance to proteolytic hydrolysis and limitless potential for diversification, γ-AApeptides may emerge as a new class of peptidomimetics to modulate RNA-protein interactions.
Collapse
Affiliation(s)
- Youhong Niu
- Department of Chemistry, University of South Florida, 4202 E. Fowler Ave., Tampa, FL 33620, USA
| | | | | | | | | |
Collapse
|
67
|
Lalonde MS, Lobritz MA, Ratcliff A, Chamanian M, Athanassiou Z, Tyagi M, Wong J, Robinson JA, Karn J, Varani G, Arts EJ. Inhibition of both HIV-1 reverse transcription and gene expression by a cyclic peptide that binds the Tat-transactivating response element (TAR) RNA. PLoS Pathog 2011; 7:e1002038. [PMID: 21625572 PMCID: PMC3098202 DOI: 10.1371/journal.ppat.1002038] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2010] [Accepted: 03/04/2011] [Indexed: 11/18/2022] Open
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 IC50 ∼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. The HIV-1 transactivator protein (Tat), together with the elongation factor
P-TEFb binds to an HIV-1 RNA secondary structure in the 5′-UTRs of nascent
viral mRNAs (TAR) and promotes transcription elongation. This process has been
an attractive target for drug development but previous inhibitors that bind
either Tat or TAR have been plagued by poor inhibition of virus replication,
limited cell penetration, and off-target effects. In this article, we describe a
series of rationally designed cyclic peptides that block Tat-TAR interactions.
L50, the most potent of these compounds, inhibits a wide range of HIV-1 strains
from around the world. Remarkably, L50 inhibits two distinct steps in the HIV-1
lifecycle. As expected, L50 inhibits Tat-dependent HIV-1 transcription, but the
majority of its anti-HIV activity is due to a block in reverse transcription,
i.e. synthesis of the proviral DNA from the RNA genome. L50 inhibition of
reverse transcription reveals an important role for TAR RNA during reverse
transcription as well as providing one of first examples of a drug with a dual
mechanism of action.
Collapse
Affiliation(s)
- Matthew S. Lalonde
- Department of Biochemistry, Case Western
Reserve University, Cleveland, Ohio, United States of America
| | - Michael A. Lobritz
- Department of Molecular Biology and
Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of
America
| | - Annette Ratcliff
- Department of Molecular Biology and
Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of
America
| | - Mastooreh Chamanian
- Department of Molecular Biology and
Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of
America
| | - Zafiria Athanassiou
- Department of Chemistry and Department of
Biochemistry, University of Washington, Seattle, Washington, United States of
America
| | - Mudit Tyagi
- Department of Molecular Biology and
Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of
America
| | - Julian Wong
- Department of Molecular Biology and
Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of
America
| | - John A. Robinson
- Department of Chemistry, University of Zurich,
Zurich, Switzerland
| | - Jonathan Karn
- Department of Molecular Biology and
Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of
America
| | - Gabriele Varani
- Department of Chemistry and Department of
Biochemistry, University of Washington, Seattle, Washington, United States of
America
| | - Eric J. Arts
- Department of Molecular Biology and
Microbiology, Case Western Reserve University, Cleveland, Ohio, United States of
America
- Division of Infectious Diseases, Department of
Medicine, Case Western Reserve University, Cleveland, Ohio, United States of
America
- * E-mail:
| |
Collapse
|
68
|
Lu J, Kadakkuzha BM, Zhao L, Fan M, Qi X, Xia T. Dynamic ensemble view of the conformational landscape of HIV-1 TAR RNA and allosteric recognition. Biochemistry 2011; 50:5042-57. [PMID: 21553929 DOI: 10.1021/bi200495d] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
RNA conformational dynamics and the resulting structural heterogeneity play an important role in RNA functions, e.g., recognition. Recognition of HIV-1 TAR RNA has been proposed to occur via a conformational capture mechanism. Here, using ultrafast time-resolved fluorescence spectroscopy, we have probed the complexity of the conformational landscape of HIV-1 TAR RNA and monitored the position-dependent changes in the landscape upon binding of a Tat protein-derived peptide and neomycin B. In the ligand-free state, the TAR RNA samples multiple families of conformations with various degrees of base stacking around the three-nucleotide bulge region. Some subpopulations partially resemble those ligand-bound states, but the coaxially stacked state is below the detection limit. When Tat or neomycin B binds, the bulge region as an ensemble undergoes a conformational transition in a position-dependent manner. Tat and neomycin B induce mutually exclusive changes in the TAR RNA underlying the mechanism of allosteric inhibition at an ensemble level with residue-specific details. Time-resolved anisotropy decay measurements revealed picosecond motions of bases in both ligand-free and ligand-bound states. Mutation of a base pair at the bulge--stem junction has differential effects on the conformational distributions of the bulge bases. A dynamic model of the ensemble view of the conformational landscape for HIV-1 TAR RNA is proposed, and the implication of the general mechanism of RNA recognition and its impact on RNA-based therapeutics are discussed.
Collapse
Affiliation(s)
- Jia Lu
- Department of Molecular and Cell Biology, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | | | | | | | | | | |
Collapse
|
69
|
Davis DR, Seth PP. Therapeutic targeting of HCV internal ribosomal entry site RNA. Antivir Chem Chemother 2011; 21:117-28. [PMID: 21233533 DOI: 10.3851/imp1693] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
HCV infection is a significant human disease, leading to liver cirrhosis and cancer, and killing >10,000 people in the US annually. Translation of the viral RNA genome is initiated by ribosomal binding to a highly structured RNA element, the internal ribosomal entry site (IRES), which presents a novel target for therapeutic intervention. We will first discuss studies of oligonucleotide therapeutics targeting various regions of the 340-nucleotide IRES, many of which have effectively blocked IRES function in vitro and are active against virus replication in cell culture. Although low nanomolar potencies have been obtained for DNA- and RNA-based molecules, stability and drug delivery challenges remain to be addressed for these particular HCV compounds. Several classes of small molecule inhibitors have been identified from screening protocols or designed from established RNA therapeutic scaffolds. In particular, small molecule IRES inhibitors based on a benzimidazole scaffold bind specifically to the IRES, and inhibit viral replication in cell culture at micromolar concentrations with low toxicity. The structure of the RNA target in complex with a representative member of these small molecule inhibitors demonstrates that a large RNA conformational change occurs upon inhibitor binding. The RNA complex shows how the inhibitor alters the global RNA structure and provides a framework for structure-based drug design of novel HCV therapeutics.
Collapse
Affiliation(s)
- Darrell R Davis
- Department of Medicinal Chemistry, University of Utah, Salt Lake City, UT, USA.
| | | |
Collapse
|
70
|
Huang W, Varani G, Drobny GP. 13C/15N-19F intermolecular REDOR NMR study of the interaction of TAR RNA with Tat peptides. J Am Chem Soc 2010; 132:17643-5. [PMID: 21105680 PMCID: PMC3238802 DOI: 10.1021/ja1051439] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The complex of the HIV TAR RNA with the viral regulatory protein Tat is of considerable interest, but the plasticity of this interaction has made it impossible so far to establish the structure of that complex. In order to explore a new approach to obtain structural information on protein-RNA complexes, we performed (13)C/(15)N-(19)F REDOR NMR experiments in the solid state on TAR bound to a peptide comprising the RNA-binding section of Tat. A critical arginine in the peptide was uniformly (13)C and (15)N labeled, and 5-fluorouridine was incorporated at the U23 position of TAR. REDOR irradiation resulted in dephasing of the (13)C and (15)N resonances, indicating the proximity of the U23(5F)-C and U23(5F)-N spin pairs. Best fits to the REDOR data show the U23(5F)-C distances and the U23(5F)-N distances are in good agreement with the distances obtained from solution NMR structures of partial complexes of Tat with TAR. These results demonstrate that it is possible to study protein-RNA complexes using solid-state REDOR NMR measurements, adding to a growing list of solid state techniques for studying protein-nucleic acid complexes.
Collapse
Affiliation(s)
- Wei Huang
- Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195, United States
| | | | | |
Collapse
|
71
|
Fulle S, Christ NA, Kestner E, Gohlke H. HIV-1 TAR RNA spontaneously undergoes relevant apo-to-holo conformational transitions in molecular dynamics and constrained geometrical simulations. J Chem Inf Model 2010; 50:1489-501. [PMID: 20726603 DOI: 10.1021/ci100101w] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
We report all-atom molecular dynamics and replica exchange molecular dynamics simulations on the unbound human immunodeficiency virus type-1 (HIV-1) transactivation responsive region (TAR) RNA structure and three TAR RNA structures in bound conformations of, in total, approximately 250 ns length. We compare the extent of observed conformational sampling with that of the conceptually simpler and computationally much cheaper constrained geometrical simulation approach framework rigidity optimized dynamic algorithm (FRODA). Atomic fluctuations obtained by replica-exchange molecular dynamics (REMD) simulations agree quantitatively with those obtained by molecular dynamics (MD) and FRODA simulations for the unbound TAR structure. Regarding the stereochemical quality of the generated conformations, backbone torsion angles and puckering modes of the sugar-phosphate backbone were reproduced equally well by MD and REMD simulations, but further improvement is needed in the case of FRODA simulations. Essential dynamics analysis reveals that all three simulation approaches show a tendency to sample bound conformations when starting from the unbound TAR structure, with MD and REMD simulations being superior with respect to FRODA. These results are consistent with the experimental view that bound TAR RNA conformations are transiently sampled in the free ensemble, following a conformation selection model. The simulation-generated TAR RNA conformations have been successfully used as receptor structures for docking. This finding has important implications for RNA-ligand docking in that docking into an ensemble of simulation-generated RNA structures is shown to be a valuable means to cope with large apo-to-holo conformational transitions of the receptor structure.
Collapse
Affiliation(s)
- Simone Fulle
- Department of Biological Sciences, Goethe-University, Frankfurt, Germany
| | | | | | | |
Collapse
|
72
|
Davidson A, Patora-Komisarska K, Robinson JA, Varani G. Essential structural requirements for specific recognition of HIV TAR RNA by peptide mimetics of Tat protein. Nucleic Acids Res 2010; 39:248-56. [PMID: 20724442 PMCID: PMC3017588 DOI: 10.1093/nar/gkq713] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
The pharmacological disruption of the interaction between the HIV Tat protein and its cognate transactivation response RNA (TAR) would generate novel anti-viral drugs with a low susceptibility to drug resistance, but efforts to discover ligands with sufficient potency to warrant pharmaceutical development have been unsuccessful. We have previously described a family of structurally constrained β-hairpin peptides that potently inhibits viral growth in HIV-infected cells. The nuclear magnetic resonance (NMR) structure of an inhibitory complex revealed that the peptide makes intimate contacts with the 3-nt bulge and the upper helix of the RNA hairpin, but that a single residue contacts the apical loop where recruitment of the essential cellular co-factor cyclin T1 occurs. Attempting to extend the peptide to form more interactions with the RNA loop, we examined a library of longer peptides and achieved >6-fold improvement in affinity. The structure of TAR bound to one of the extended peptides reveals that the peptide slides down the major groove of the RNA, relative to our design, in order to maintain critical interactions with TAR. These conserved contacts involve three amino acid side chains and identify critical interaction points required for potent and specific binding to TAR RNA. They constitute a template of essential interactions required for inhibition of this RNA.
Collapse
Affiliation(s)
- Amy Davidson
- Department of Chemistry, University of Washington, Seattle, WA 98195, USA
| | | | | | | |
Collapse
|
73
|
Li Y, Shen J, Sun X, Li W, Liu G, Tang Y. Accuracy Assessment of Protein-Based Docking Programs against RNA Targets. J Chem Inf Model 2010; 50:1134-46. [DOI: 10.1021/ci9004157] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yaozong Li
- Department of Pharmaceutical Sciences, School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China
| | - Jie Shen
- Department of Pharmaceutical Sciences, School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China
| | - Xianqiang Sun
- Department of Pharmaceutical Sciences, School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China
| | - Weihua Li
- Department of Pharmaceutical Sciences, School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China
| | - Guixia Liu
- Department of Pharmaceutical Sciences, School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China
| | - Yun Tang
- Department of Pharmaceutical Sciences, School of Pharmacy, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237, China
| |
Collapse
|
74
|
Kondo J, Westhof E. Base pairs and pseudo pairs observed in RNA-ligand complexes. J Mol Recognit 2010; 23:241-52. [PMID: 19701919 DOI: 10.1002/jmr.978] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Previously, a geometric nomenclature was proposed in which RNA base pairs were classified by their interaction edges (Watson-Crick, Hoogsteen or sugar-edge) and the glycosidic bond orientations relative to the hydrogen bonds formed (cis or trans). Here, base pairs and pseudo pairs observed in RNA-ligand complexes are classified in a similar manner. Twenty-one basic geometric families are geometrically possible (18 for base pairs formed between a nucleic acid base and a ligand containing heterocycle and 3 families for pseudo pairs). Of those, 16 of them have been observed in X-ray and/or NMR structures.
Collapse
Affiliation(s)
- Jiro Kondo
- Architecture et Réactivité de l'ARN, Université de Strasbourg, Institut de Biologie Moléculaire et Cellulaire, CNRS, 15 rue René Descartes, 67084 Strasbourg, France
| | | |
Collapse
|
75
|
Abstract
Translation of the hepatitis C virus (HCV) RNA is initiated from a highly structured internal ribosomal entry site (IRES) in the 5' untranslated region (5' UTR) of the RNA genome. An important structural feature of the native RNA is an approximately 90 degrees helical bend localized to domain IIa that positions the apical loop of domain IIb of the IRES near the 40S ribosomal E-site to promote eIF2-GDP release, facilitating 80S ribosome assembly. We report here the NMR structure of a domain IIa construct in complex with a potent small-molecule inhibitor of HCV replication. Molecular dynamics refinement in explicit solvent and subsequent energetic analysis indicated that each inhibitor stereoisomer bound with comparable affinity and in an equivalent binding mode. The in silico analysis was substantiated by fluorescence-based assays showing that the relative binding free energies differed by only 0.7 kcal/mol. Binding of the inhibitor displaces key nucleotide residues within the bulge region, effecting a major conformational change that eliminates the bent RNA helical trajectory, providing a mechanism for the antiviral activity of this inhibitor class.
Collapse
|
76
|
Tan JJ, Cong XJ, Hu LM, Wang CX, Jia L, Liang XJ. Therapeutic strategies underpinning the development of novel techniques for the treatment of HIV infection. Drug Discov Today 2010; 15:186-97. [PMID: 20096804 DOI: 10.1016/j.drudis.2010.01.004] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2009] [Revised: 11/21/2009] [Accepted: 01/14/2010] [Indexed: 11/28/2022]
Abstract
The HIV replication cycle offers multiple targets for chemotherapeutic intervention, including the viral exterior envelope glycoprotein, gp120; viral co-receptors CXCR4 and CCR5; transmembrane glycoprotein, gp41; integrase; reverse transcriptase; protease and so on. Most currently used anti-HIV drugs are reverse transcriptase inhibitors or protease inhibitors. The expanding application of simulation to drug design combined with experimental techniques have developed a large amount of novel inhibitors that interact specifically with targets besides transcriptase and protease. This review presents details of the anti-HIV inhibitors discovered with computer-aided approaches and provides an overview of the recent five-year achievements in the treatment of HIV infection and the application of computational methods to current drug design.
Collapse
Affiliation(s)
- Jian J Tan
- College of Life Science and Bio-engineering, Beijing University of Technology, Beijing 100124, China
| | | | | | | | | | | |
Collapse
|
77
|
Abstract
Bacterial ribosomal RNA is the target of clinically important antibiotics, while biologically important RNAs in viral and eukaryotic genomes present a range of potential drug targets. The physicochemical properties of RNA present difficulties for medicinal chemistry, particularly when oral availability is needed. Peptidic ligands and analysis of their RNA-binding properties are providing insight into RNA recognition. RNA-binding ligands include far more chemical classes than just aminoglycosides. Chemical functionalities from known RNA-binding small molecules are being exploited in fragment- and ligand-based projects. While targeting of RNA for drug design is very challenging, continuing advances in our understanding of the principles of RNA–ligand interaction will be necessary to realize the full potential of this class of targets.
Collapse
|
78
|
Zhang Q, Al-Hashimi HM. Domain-elongation NMR spectroscopy yields new insights into RNA dynamics and adaptive recognition. RNA (NEW YORK, N.Y.) 2009; 15:1941-8. [PMID: 19776156 PMCID: PMC2764479 DOI: 10.1261/rna.1806909] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
By simplifying the interpretation of nuclear magnetic resonance spin relaxation and residual dipolar couplings data, recent developments involving the elongation of RNA helices are providing new atomic insights into the dynamical properties that allow RNA structures to change functionally and adaptively. Domain elongation, in concert with spin relaxation measurements, has allowed the detailed characterization of a hierarchical network of local and collective motional modes occurring at nanosecond timescale that mirror the structural rearrangements that take place following adaptive recognition. The combination of domain elongation with residual dipolar coupling measurements has allowed the experimental three-dimensional visualization of very large amplitude rigid-body helix motions in HIV-1 transactivation response element (TAR) that trace out a highly choreographed trajectory in which the helices twist and bend in a correlated manner. The dynamic trajectory allows unbound TAR to sample many of its ligand bound conformations, indicating that adaptive recognition occurs by "conformational selection" rather than "induced fit." These studies suggest that intrinsic flexibility plays essential roles directing RNA conformational changes along specific pathways.
Collapse
Affiliation(s)
- Qi Zhang
- Department of Chemistry and Biochemistry, University of California at Los Angeles, Los Angeles, California, 90095, USA
| | | |
Collapse
|
79
|
Ferner J, Suhartono M, Breitung S, Jonker HRA, Hennig M, Wöhnert J, Göbel M, Schwalbe H. Structures of HIV TAR RNA-ligand complexes reveal higher binding stoichiometries. Chembiochem 2009; 10:1490-4. [PMID: 19444830 DOI: 10.1002/cbic.200900220] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Target TAR by NMR: Tripeptides containing arginines as terminal residues and non-natural amino acids as central residues are good leads for drug design to target the HIV trans-activation response element (TAR). The structural characterization of the RNA-ligand complex by NMR spectroscopy reveals two specific binding sites that are located at bulge residue U23 and around the pyrimidine-stretch U40-C41-U42 directly adjacent to the bulge.
Collapse
Affiliation(s)
- Jan Ferner
- Institut für Organische Chemie und Chemische Biologie, Zentrum für Biomolekulare Magnetische Resonanz (BMRZ), Johann Wolfgang Goethe-Universität Frankfurt am Main, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main, Germany
| | | | | | | | | | | | | | | |
Collapse
|
80
|
Simultaneous recognition of HIV-1 TAR RNA bulge and loop sequences by cyclic peptide mimics of Tat protein. Proc Natl Acad Sci U S A 2009; 106:11931-6. [PMID: 19584251 DOI: 10.1073/pnas.0900629106] [Citation(s) in RCA: 138] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The interaction of the HIV-1 transactivator protein Tat with its transactivation response (TAR) RNA is an essential step in viral replication and therefore an attractive target for developing antivirals with new mechanisms of action. Numerous compounds that bind to the 3-nt bulge responsible for binding Tat have been identified in the past, but none of these molecules had sufficient potency to warrant pharmaceutical development. We have discovered conformationally-constrained cyclic peptide mimetics of Tat that are specific nM inhibitors of the Tat-TAR interaction by using a structure-based approach. The lead peptides are nearly as active as the antiviral drug nevirapine against a variety of clinical isolates in human lymphocytes. The NMR structure of a peptide-RNA complex reveals that these molecules interfere with the recruitment to TAR of both Tat and the essential cellular cofactor transcription elongation factor-b (P-TEFb) by binding simultaneously at the RNA bulge and apical loop, forming an unusually deep pocket. This structure illustrates additional principles in RNA recognition: RNA-binding molecules can achieve specificity by interacting simultaneously with multiple secondary structure elements and by inducing the formation of deep binding pockets in their targets. It also provides insight into the P-TEFb binding site and a rational basis for optimizing the promising antiviral activity observed for these cyclic peptides.
Collapse
|
81
|
Bryson DI, Zhang W, Ray WK, Santos WL. Screening of a branched peptide library with HIV-1 TAR RNA. MOLECULAR BIOSYSTEMS 2009; 5:1070-3. [PMID: 19668873 DOI: 10.1039/b904304g] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The recognition that RNA is more than just an intermediate in the information transfer from genetic code to fully functional protein has placed it at the forefront of chemical research. RNA is important because of its vital role in regulating transcription, translation, splicing, replication and catalysis. Consequently, molecules that can bind to RNA and control its function have potential as powerful tools in biology and medicine. Herein, we report the discovery of HIV-1 TAR RNA-selective ligands using an on-bead screening of a library of 4096 branched peptides.
Collapse
Affiliation(s)
- David I Bryson
- Virginia Tech, Department of Chemistry, Blacksburg, VA 24061, USA
| | | | | | | |
Collapse
|
82
|
Bodoor K, Boyapati V, Gopu V, Boisdore M, Allam K, Miller J, Treleaven WD, Weldeghiorghis T, Aboul-ela F. Design and Implementation of an Ribonucleic Acid (RNA) Directed Fragment Library. J Med Chem 2009; 52:3753-61. [DOI: 10.1021/jm9000659] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Khaled Bodoor
- Departments of Biological Sciences and Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, and Department of Physics, University of Jordan, Amman 11942, Jordan
| | - Vamsi Boyapati
- Departments of Biological Sciences and Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, and Department of Physics, University of Jordan, Amman 11942, Jordan
| | - Vikram Gopu
- Departments of Biological Sciences and Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, and Department of Physics, University of Jordan, Amman 11942, Jordan
| | - Marietta Boisdore
- Departments of Biological Sciences and Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, and Department of Physics, University of Jordan, Amman 11942, Jordan
| | - Kiran Allam
- Departments of Biological Sciences and Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, and Department of Physics, University of Jordan, Amman 11942, Jordan
| | - Janae Miller
- Departments of Biological Sciences and Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, and Department of Physics, University of Jordan, Amman 11942, Jordan
| | - W. Dale Treleaven
- Departments of Biological Sciences and Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, and Department of Physics, University of Jordan, Amman 11942, Jordan
| | - Thomas Weldeghiorghis
- Departments of Biological Sciences and Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, and Department of Physics, University of Jordan, Amman 11942, Jordan
| | - Fareed Aboul-ela
- Departments of Biological Sciences and Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, and Department of Physics, University of Jordan, Amman 11942, Jordan
| |
Collapse
|
83
|
Lee SJ, Hyun S, Kieft JS, Yu J. An approach to the construction of tailor-made amphiphilic peptides that strongly and selectively bind to hairpin RNA targets. J Am Chem Soc 2009; 131:2224-30. [PMID: 19199621 DOI: 10.1021/ja807609m] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The hairpin RNA motif is one of the most frequently observed secondary structures and is often targeted by therapeutic agents. An amphiphilic peptide with seven lysine and eight leucine residues and its derivatives were designed for use as ligands against RNA hairpin motifs. We hypothesized that variations in both the hydrophobic leucine-rich and hydrophilic lysine-rich spheres of these amphiphilic peptides would create extra attractive interactions with hairpin RNA targets. A series of alanine-scanned peptides were probed to identify the most influential lysine residues in the hydrophilic sphere. The binding affinities of these modified peptides with several hairpins, such as RRE, TAR from HIV, a short hairpin from IRES of HCV, and a hairpin from the 16S A-site stem from rRNA, were determined. Since the hairpin from IRES of HCV was the most susceptible to the initial series of alanine-scanned peptides, studies investigating how further variations in the peptides effect binding employed the IRES hairpin. Next, the important Lys residues were substituted by shorter chain amines, such as ornithine, to place the peptide deeper into the hairpin groove. In a few cases, a 70-fold improved binding was observed for peptides that contained the specifically located shorter amine side chains. To further explore changes in binding affinities brought about by alterations in the hydrophobic sphere, tryptophan residues were introduced in place of leucine. A few peptides with tryptophan in specific positions also displayed 70-fold improved binding affinities. Finally, double mutant peptides incorporating both specifically located shorter amine side chains in the hydrophilic region and tryptophan residues in the hydrophobic region were synthesized. The binding affinities of peptides containing the simple double modification were observed to be 80 times lower, and their binding specificities were increased 40-fold. The results of this effort provide important information about strategies that can be used to prepare peptides that both strongly and selectively target hairpin RNAs. Specifically, the findings indicate that tailor-made amphiphilic peptide ligands against certain hairpin RNAs can be obtained if the RNA target possesses a deep groove in which both the hydrophobic and hydrophilic spheres of the peptide interact.
Collapse
Affiliation(s)
- Su Jin Lee
- Department of Chemistry and Education, Seoul National University, Seoul 151-748, Korea
| | | | | | | |
Collapse
|
84
|
Labuda LP, Pushechnikov A, Disney MD. Small molecule microarrays of RNA-focused peptoids help identify inhibitors of a pathogenic group I intron. ACS Chem Biol 2009; 4:299-307. [PMID: 19278238 DOI: 10.1021/cb800313m] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Peptoids that inhibit the group I intron RNA from Candida albicans, an opportunistic pathogen that kills immunocompromised hosts, have been identified using microarrays. The arrayed peptoid library was constructed using submonomers with moieties similar to ones found in small molecules known to bind RNA. Library members that passed quality control analysis were spotted onto a microarray and screened for binding to the C. albicans group I intron ribozyme. Each ligand binder identified from microarray-based screening inhibited self-splicing in the presence of 1 mM nucleotide concentration of bulk yeast tRNA with IC(50)'s between 150 and 2200 microM. The binding signals and the corresponding IC(50)'s were used to identify features in the peptoids that predispose them for RNA binding. After statistical analysis of the peptoids' structures that bind, a second generation of inhibitors was constructed using these important features; all second generation inhibitors have improved potencies with IC(50)'s of <100 microM. The most potent inhibitor is composed of one phenylguanidine and three tryptamine submonomers and has an IC(50) of 31 microM. This compound is 6-fold more potent than pentamidine, a clinically used drug that inhibits self-splicing. These results show that (i) modulators of RNA function can be identified by designing RNA-focused chemical libraries and screening them via microarray; (ii) statistical analysis of ligand binders can identify features in leads that predispose them for binding to their targets; and (iii) features can then be programmed into second generation inhibitors to design ligands with improved potencies.
Collapse
Affiliation(s)
- Lucas P. Labuda
- Department of Chemistry and The Center of Excellence in Bioinformatics and Life Sciences, University at Buffalo, 657 Natural Sciences Complex, Buffalo, New York 14260
| | - Alexei Pushechnikov
- Department of Chemistry and The Center of Excellence in Bioinformatics and Life Sciences, University at Buffalo, 657 Natural Sciences Complex, Buffalo, New York 14260
| | - Matthew D. Disney
- Department of Chemistry and The Center of Excellence in Bioinformatics and Life Sciences, University at Buffalo, 657 Natural Sciences Complex, Buffalo, New York 14260
| |
Collapse
|
85
|
Frank AT, Stelzer AC, Al-Hashimi HM, Andricioaei I. Constructing RNA dynamical ensembles by combining MD and motionally decoupled NMR RDCs: new insights into RNA dynamics and adaptive ligand recognition. Nucleic Acids Res 2009; 37:3670-9. [PMID: 19369218 PMCID: PMC2699496 DOI: 10.1093/nar/gkp156] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
We describe a strategy for constructing atomic resolution dynamical ensembles of RNA molecules, spanning up to millisecond timescales, that combines molecular dynamics (MD) simulations with NMR residual dipolar couplings (RDC) measured in elongated RNA. The ensembles are generated via a Monte Carlo procedure by selecting snap-shot from an MD trajectory that reproduce experimentally measured RDCs. Using this approach, we construct ensembles for two variants of the transactivation response element (TAR) containing three (HIV-1) and two (HIV-2) nucleotide bulges. The HIV-1 TAR ensemble reveals significant mobility in bulge residues C24 and U25 and to a lesser extent U23 and neighboring helical residue A22 that give rise to large amplitude spatially correlated twisting and bending helical motions. Omission of bulge residue C24 in HIV-2 TAR leads to a significant reduction in both the local mobility in and around the bulge and amplitude of inter-helical bending motions. In contrast, twisting motions of the helices remain comparable in amplitude to HIV-1 TAR and spatial correlations between them increase significantly. Comparison of the HIV-1 TAR dynamical ensemble and ligand bound TAR conformations reveals that several features of the binding pocket and global conformation are dynamically preformed, providing support for adaptive recognition via a ‘conformational selection’ type mechanism.
Collapse
Affiliation(s)
- Aaron T Frank
- Department of Chemistry, University of California Irvine, 1102 Natural Sciences 2, Irvine, CA 92697, USA
| | | | | | | |
Collapse
|
86
|
Bardaro MF, Shajani Z, Patora-Komisarska K, Robinson JA, Varani G. How binding of small molecule and peptide ligands to HIV-1 TAR alters the RNA motional landscape. Nucleic Acids Res 2009; 37:1529-40. [PMID: 19139066 PMCID: PMC2655691 DOI: 10.1093/nar/gkn1074] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
The HIV-1 TAR RNA represents a well-known paradigm to study the role of dynamics and conformational change in RNA function. This regulatory RNA changes conformation in response to binding of Tat protein and of a variety of peptidic and small molecule ligands, indicating that its conformational flexibility and intrinsic dynamics play important roles in molecular recognition. We have used 13C NMR relaxation experiments to examine changes in the motional landscape of HIV-1 TAR in the presence of three ligands of different affinity and specificity. The ligands are argininamide, a linear peptide mimic of the Tat basic domain and a cyclic peptide that potently inhibits Tat-dependent activation of transcription. All three molecules induce the same motional characteristics within the three nucleotides bulge that represents the Tat-binding site. However, the cyclic peptide has a unique motional signature in the apical loop, which represents a binding site for the essential host co-factor cyclin T1. These results suggest that all peptidic mimics of Tat induce the same dynamics in TAR within this protein binding site. However, the new cyclic peptide mimic of Tat represents a new class of ligands with a unique effect on the dynamics and the structure of the apical loop.
Collapse
Affiliation(s)
- Michael F Bardaro
- Department of Chemistry, University of Washington, Seattle, WA 98195-1700, USA
| | | | | | | | | |
Collapse
|
87
|
Lapidot A, Berchanski A, Borkow G. Insight into the mechanisms of aminoglycoside derivatives interaction with HIV-1 entry steps and viral gene transcription. FEBS J 2008; 275:5236-57. [PMID: 18803669 DOI: 10.1111/j.1742-4658.2008.06657.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
In recent years, based on peptide models of HIV-1 RNA binding, NMR structures of Tat-responsive element-ligand complexes and aminoglycoside-RNA interactions, and HIV-1 Tat structure, we have designed and synthesized aminoglycoside-arginine conjugates (AACs) and aminoglycoside poly-arginine conjugates (APACs), to serve as Tat mimetics. These novel molecules inhibit HIV-1 infectivity with 50% effective concentration values in the low micromolar range, the most potent compounds being the hexa-arginine-neomycin B and nona-D-arginine-neomycin conjugates. Importantly, these compounds, in addition to acting as Tat antagonists, inhibit HIV-1 infectivity by blocking several steps in HIV-1 cell entry. The AACs and APACs inhibit HIV-1 cell entry by interacting with gp120 at the CD4-binding site, by interacting with CXCR4 at the binding site of the CXCR4 mAb 12G5, and apparently by interacting with transient structures of the ectodomain of gp41. In the current review, we discuss the mechanisms of anti-HIV-1 activities of these AACs, APACs and other aminoglycoside derivatives in detail. Targeting several key processes in the viral life cycle by the same compound not only may increase its antiviral efficacy, but more importantly, may reduce the capacity of the virus to develop resistance to the compound. AACs and APACs may thus serve as leading compounds for the development of multitargeting novel HIV-1 inhibitors.
Collapse
Affiliation(s)
- Aviva Lapidot
- Department of Organic Chemistry, The Weizmann Institute of Science, Rehovot, Israel.
| | | | | |
Collapse
|
88
|
Pang R, Zhang C, Yuan D, Yang M. Design and SAR of new substituted purines bearing aryl groups at N9 position as HIV-1 Tat–TAR interaction inhibitors. Bioorg Med Chem 2008; 16:8178-86. [DOI: 10.1016/j.bmc.2008.07.043] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2008] [Revised: 07/15/2008] [Accepted: 07/16/2008] [Indexed: 11/30/2022]
|
89
|
Characterizing complex dynamics in the transactivation response element apical loop and motional correlations with the bulge by NMR, molecular dynamics, and mutagenesis. Biophys J 2008; 95:3906-15. [PMID: 18621815 DOI: 10.1529/biophysj.108.140285] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The HIV-1 transactivation response element (TAR) RNA binds a variety of proteins and is a target for developing anti-HIV therapies. TAR has two primary binding sites: a UCU bulge and a CUGGGA apical loop. We used NMR residual dipolar couplings, carbon spin relaxation (R(1) and R(2)), and relaxation dispersion (R(1rho)) in conjunction with molecular dynamics and mutagenesis to characterize the dynamics of the TAR apical loop and investigate previously proposed long-range interactions with the distant bulge. Replacement of the wild-type apical loop with a UUCG loop did not significantly affect the structural dynamics at the bulge, indicating that the apical loop and the bulge act largely as independent dynamical recognition centers. The apical loop undergoes complex dynamics at multiple timescales that are likely important for adaptive recognition: U31 and G33 undergo limited motions, G32 is highly flexible at picosecond-nanosecond timescales, and G34 and C30 form a dynamic Watson-Crick basepair in which G34 and A35 undergo a slow (approximately 30 mus) likely concerted looping in and out motion, with A35 also undergoing large amplitude motions at picosecond-nanosecond timescales. Our study highlights the power of combining NMR, molecular dynamics, and mutagenesis in characterizing RNA dynamics.
Collapse
|
90
|
Guilbert C, James TL. Docking to RNA via root-mean-square-deviation-driven energy minimization with flexible ligands and flexible targets. J Chem Inf Model 2008; 48:1257-68. [PMID: 18510306 DOI: 10.1021/ci8000327] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Structure-based drug design is now well-established for proteins as a key first step in the lengthy process of developing new drugs. In many ways, RNA may be a better target to treat disease than a protein because it is upstream in the translation pathway, so inhibiting a single mRNA molecule could prevent the production of thousands of protein gene products. Virtual screening is often the starting point for structure-based drug design. However, computational docking of a small molecule to RNA seems to be more challenging than that to protein due to the higher intrinsic flexibility and highly charged structure of RNA. Previous attempts at docking to RNA showed the need for a new approach. We present here a novel algorithm using molecular simulation techniques to account for both nucleic acid and ligand flexibility. In this approach, with both the ligand and the receptor permitted some flexibility, they can bind one another via an induced fit, as the flexible ligand probes the surface of the receptor. A possible ligand can explore a low-energy path at the surface of the receptor by carrying out energy minimization with root-mean-square-distance constraints. Our procedure was tested on 57 RNA complexes (33 crystal and 24 NMR structures); this is the largest data set to date to reproduce experimental RNA binding poses. With our procedure, the lowest-energy conformations reproduced the experimental binding poses within an atomic root-mean-square deviation of 2.5 A for 74% of tested complexes.
Collapse
Affiliation(s)
- Christophe Guilbert
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94158-2517, USA
| | | |
Collapse
|
91
|
Radhakrishnan ML, Tidor B. Optimal drug cocktail design: methods for targeting molecular ensembles and insights from theoretical model systems. J Chem Inf Model 2008; 48:1055-73. [PMID: 18505239 DOI: 10.1021/ci700452r] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Drug resistance is a significant obstacle in the effective treatment of diseases with rapidly mutating targets, such as AIDS, malaria, and certain forms of cancer. Such targets are remarkably efficient at exploring the space of functional mutants and at evolving to evade drug binding while still maintaining their biological role. To overcome this challenge, drug regimens must be active against potential target variants. Such a goal may be accomplished by one drug molecule that recognizes multiple variants or by a drug "cocktail"--a small collection of drug molecules that collectively binds all desired variants. Ideally, one wants the smallest cocktail possible due to the potential for increased toxicity with each additional drug. Therefore, the task of designing a regimen for multiple target variants can be framed as an optimization problem--find the smallest collection of molecules that together "covers" the relevant target variants. In this work, we formulate and apply this optimization framework to theoretical model target ensembles. These results are analyzed to develop an understanding of how the physical properties of a target ensemble relate to the properties of the optimal cocktail. We focus on electrostatic variation within target ensembles, as it is one important mechanism by which drug resistance is achieved. Using integer programming, we systematically designed optimal cocktails to cover model target ensembles. We found that certain drug molecules covered much larger regions of target space than others, a phenomenon explained by theory grounded in continuum electrostatics. Molecules within optimal cocktails were often dissimilar, such that each drug was responsible for binding variants with a certain electrostatic property in common. On average, the number of molecules in the optimal cocktails correlated with the number of variants, the differences in the variants' electrostatic properties at the binding interface, and the level of binding affinity required. We also treated cases in which a subset of target variants was to be avoided, modeling the common challenge of closely related host molecules that may be implicated in drug toxicity. Such decoys generally increased the size of the required cocktail and more often resulted in infeasible optimizations. Taken together, this work provides practical optimization methods for the design of drug cocktails and a theoretical, physics-based framework through which useful insights can be achieved.
Collapse
Affiliation(s)
- Mala L Radhakrishnan
- Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA
| | | |
Collapse
|
92
|
Affiliation(s)
- Jason R Thomas
- Department of Chemistry, Roger Adams Laboratory, University of Illinois, Urbana, Illinois 61822, USA
| | | |
Collapse
|
93
|
Suhartono M, Weidlich M, Stein T, Karas M, Dürner G, Göbel MW. Synthesis of Non-Natural Aromatic α-Amino Acids by a Heck Reaction. European J Org Chem 2008. [DOI: 10.1002/ejoc.200701124] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
94
|
Ludwig V, Krebs A, Stoll M, Dietrich U, Ferner J, Schwalbe H, Scheffer U, Dürner G, Göbel MW. Tripeptides from synthetic amino acids block the Tat-TAR association and slow down HIV spread in cell cultures. Chembiochem 2008; 8:1850-6. [PMID: 17886825 DOI: 10.1002/cbic.200700232] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Non-natural amino acids with aromatic or heteroaromatic side chains were incorporated into tripeptides of the general structure Arg-X-Arg and tested as ligands of the HIV RNA element TAR. Some of these compounds could compete efficiently with the association of TAR and Tat and downregulated a TAR-controlled reporter gene in HeLa cells. Peptide 7, which contains a 2-pyrimidinyl-alkyl chain, also inhibited the spread of HIV-1 in cell cultures. NMR studies of 7 bound to HIV-2-TAR gave evidence for contacts in the bulge region.
Collapse
Affiliation(s)
- Verena Ludwig
- Institute of Organic Chemistry and Chemical Biology, Johann Wolfgang Goethe Universität Frankfurt, Max-von-Laue-Strasse 7, 60438 Frankfurt am Main, Germany
| | | | | | | | | | | | | | | | | |
Collapse
|
95
|
Zhang Q, Stelzer AC, Fisher CK, Al-Hashimi HM. Visualizing spatially correlated dynamics that directs RNA conformational transitions. Nature 2008; 450:1263-7. [PMID: 18097416 DOI: 10.1038/nature06389] [Citation(s) in RCA: 206] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2007] [Accepted: 10/18/2007] [Indexed: 01/27/2023]
Abstract
RNAs fold into three-dimensional (3D) structures that subsequently undergo large, functionally important, conformational transitions in response to a variety of cellular signals. RNA structures are believed to encode spatially tuned flexibility that can direct transitions along specific conformational pathways. However, this hypothesis has proved difficult to examine directly because atomic movements in complex biomolecules cannot be visualized in 3D by using current experimental methods. Here we report the successful implementation of a strategy using NMR that has allowed us to visualize, with complete 3D rotational sensitivity, the dynamics between two RNA helices that are linked by a functionally important trinucleotide bulge over timescales extending up to milliseconds. The key to our approach is to anchor NMR frames of reference onto each helix and thereby directly measure their dynamics, one relative to the other, using 'relativistic' sets of residual dipolar couplings (RDCs). Using this approach, we uncovered super-large amplitude helix motions that trace out a surprisingly structured and spatially correlated 3D dynamic trajectory. The two helices twist around their individual axes by approximately 53 degrees and 110 degrees in a highly correlated manner (R = 0.97) while simultaneously (R = 0.81-0.92) bending by about 94 degrees. Remarkably, the 3D dynamic trajectory is dotted at various positions by seven distinct ligand-bound conformations of the RNA. Thus even partly unstructured RNAs can undergo structured dynamics that directs ligand-induced transitions along specific predefined conformational pathways.
Collapse
Affiliation(s)
- Qi Zhang
- Department of Chemistry and Biophysics, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, USA
| | | | | | | |
Collapse
|
96
|
Nandi CK, Parui PP, Brutschy B, Scheffer U, Göbel M. Fluorescence correlation spectroscopy at single molecule level on the Tat–TAR complex and its inhibitors. Biopolymers 2008; 89:17-25. [PMID: 17764074 DOI: 10.1002/bip.20835] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The TAR element of HIV and the viral protein Tat form a molecular switch regulating transcriptional efficiency in HIV. We show that fluorescence correlation spectroscopy at the single molecule level is a powerful method to study the association between a Tat-derived peptide and TAR fragments. We also investigated the inhibition of the peptide-RNA complex by different ligands. Utilizing cross correlation measurements, the dissociation constants (K(D)) were determined. To demonstrate the important role of the bulge for the binding of Tat, we compared wt-TAR with three RNA mutants, mainly differing in the bulge region. For the TAR mutants studied at equimolar concentration of RNA and peptide (25 nM), the K(D) values are 15-35 times larger than that of wt-TAR. This gives evidence that the bulge region is the most crucial part of the TAR RNA for specific Tat binding. The IC(50) values for different inhibitors of the Tat/TAR complex both with wt-TAR and mutants have been determined. Neamine conjugate proved to be the best inhibitor of the complex formation. Our results are in agreement with earlier published data on this system using alternative biophysical and biochemical methods, respectively.
Collapse
Affiliation(s)
- Chayan Kanti Nandi
- Institut für Physikalische und Theoretische Chemie, Johann Wolfgang Goethe-Universität Frankfurt, Max-von-Laue-Str 7, D-60438 Frankfurt am Main, Germany
| | | | | | | | | |
Collapse
|
97
|
Bailor MH, Musselman C, Hansen AL, Gulati K, Patel DJ, Al-Hashimi HM. Characterizing the relative orientation and dynamics of RNA A-form helices using NMR residual dipolar couplings. Nat Protoc 2007; 2:1536-46. [PMID: 17571061 PMCID: PMC4707013 DOI: 10.1038/nprot.2007.221] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
We present a protocol for determining the relative orientation and dynamics of A-form helices in 13C/15N isotopically enriched RNA samples using NMR residual dipolar couplings (RDCs). Non-terminal Watson-Crick base pairs in helical stems are experimentally identified using NOE and trans-hydrogen bond connectivity and modeled using the idealized A-form helix geometry. RDCs measured in the partially aligned RNA are used to compute order tensors describing average alignment of each helix relative to the applied magnetic field. The order tensors are translated into Euler angles defining the average relative orientation of helices and order parameters describing the amplitude and asymmetry of interhelix motions. The protocol does not require complete resonance assignments and therefore can be implemented rapidly to RNAs much larger than those for which complete high-resolution NMR structure determination is feasible. The protocol is particularly valuable for exploring adaptive changes in RNA conformation that occur in response to biologically relevant signals. Following resonance assignments, the procedure is expected to take no more than 2 weeks of acquisition and data analysis time.
Collapse
Affiliation(s)
- Maximillian H Bailor
- Department of Chemistry & Biophysics Research Division, The University of Michigan, Ann Arbor, Michigan 48109, USA
| | | | | | | | | | | |
Collapse
|
98
|
Landes CF, Zeng Y, Liu HW, Musier-Forsyth K, Barbara PF. Single-Molecule Study of the Inhibition of HIV-1 Transactivation Response Region DNA/DNA Annealing by Argininamide. J Am Chem Soc 2007; 129:10181-8. [PMID: 17658799 DOI: 10.1021/ja071491r] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Single-molecule spectroscopy was used to examine how a model inhibitor of HIV-1, argininamide, modulates the nucleic acid chaperone activity of the nucleocapsid protein (NC) in the minus-strand transfer step of HIV-1 reverse transcription, in vitro. In minus-strand transfer, the transactivation response region (TAR) RNA of the genome is annealed to the complementary "TAR DNA" generated during minus-strand strong-stop DNA synthesis. Argininamide and its analogs are known to bind to the hairpin bulge region of TAR RNA as well as to various DNA loop structures, but its ability to inhibit the strand transfer process has only been implied. Here, we explore how argininamide modulates the annealing kinetics and secondary structure of TAR DNA. The studies reveal that the argininamide inhibitory mechanism involves a shift of the secondary structure of TAR, away from the NC-induced "Y" form, an intermediate in reverse transcription, and toward the free closed or "C" form. In addition, more potent inhibition of the loop-mediated annealing pathway than stem-mediated annealing is observed. Taken together, these data suggest a molecular mechanism wherein argininamide inhibits NC-facilitated TAR RNA/DNA annealing in vitro by interfering with the formation of key annealing intermediates.
Collapse
Affiliation(s)
- Christy F Landes
- Department of Chemistry and Biochemistry, Center for Nano and Molecular Science and Technology, The University of Texas at Austin, Austin, Texas 78712, USA
| | | | | | | | | |
Collapse
|
99
|
Casiano-Negroni A, Sun X, Al-Hashimi HM. Probing Na(+)-induced changes in the HIV-1 TAR conformational dynamics using NMR residual dipolar couplings: new insights into the role of counterions and electrostatic interactions in adaptive recognition. Biochemistry 2007; 46:6525-35. [PMID: 17488097 PMCID: PMC3319146 DOI: 10.1021/bi700335n] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Many regulatory RNAs undergo large changes in structure upon recognition of proteins and ligands, but the mechanism by which this occurs remains poorly understood. Using NMR residual dipolar coupling (RDCs), we characterized Na+-induced changes in the structure and dynamics of the bulge-containing HIV-1 transactivation response element (TAR) RNA that mirrors changes induced by small molecules bearing a different number of cationic groups. Increasing the Na+ concentration from 25 to 320 mM led to a continuous reduction in the average inter-helical bend angle (from 46 degrees to 22 degrees ), inter-helical twist angle (from 66 degrees to -18 degrees ), and inter-helix flexibility (as measured by an increase in the internal generalized degree of order from 0.56 to 0.74). Similar conformational changes were observed with Mg2+, indicating that nonspecific electrostatic interactions drive the conformational transition, although results also suggest that Na+ and Mg2+ may associate with TAR in distinct modes. The transition can be rationalized on the basis of a population-weighted average of two ensembles comprising an electrostatically relaxed bent and flexible TAR conformation that is weakly associated with counterions and a globally rigid coaxial conformation that has stronger electrostatic potential and association with counterions. The TAR inter-helical orientations that are stabilized by small molecules fall around the metal-induced conformational pathway, indicating that counterions may help predispose the TAR conformation for target recognition. Our results underscore the intricate sensitivity of RNA conformational dynamics to environmental conditions and demonstrate the ability to detect subtle conformational changes using NMR RDCs.
Collapse
Affiliation(s)
| | | | - Hashim M. Al-Hashimi
- To whom correspondence should be addressed. H. M. A.: ; telephone (734) 615 3361; fax (734) 647 4865
| |
Collapse
|
100
|
Mayer M, Lang PT, Gerber S, Madrid PB, Pinto IG, Guy RK, James TL. Synthesis and testing of a focused phenothiazine library for binding to HIV-1 TAR RNA. ACTA ACUST UNITED AC 2006; 13:993-1000. [PMID: 16984889 DOI: 10.1016/j.chembiol.2006.07.009] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2006] [Revised: 07/12/2006] [Accepted: 07/25/2006] [Indexed: 11/25/2022]
Abstract
We have synthesized a series of phenothiazine derivatives, which were used to test the structure-activity relationship of binding to HIV-1 TAR RNA. Variations from our initial compound, 2-acetylphenothiazine, focused on two moieties: ring substitutions and n-alkyl substitutions. Binding characteristics were ascertained via NMR, principally by saturation transfer difference spectra of the ligand and imino proton resonance shifts of the RNA. Both ring and alkyl substitutions manifested NMR changes upon binding. In general, the active site, while somewhat flexible, has regions that can be capitalized for increased binding through van der Waals interactions and others that can be optimized for solubility in subsequent stages of development. However, binding can be nontrivially enhanced several-fold through optimization of van der Waals and hydrophilic sites of the scaffold.
Collapse
Affiliation(s)
- Moriz Mayer
- Department of Pharmaceutical Chemistry, University of California, San Francisco, California 94158, USA
| | | | | | | | | | | | | |
Collapse
|