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Gaudin C, Nonin-Lecomte S, Tisné C, Corvaisier S, Bordeau V, Dardel F, Felden B. The tRNA-like domains of E coli and A.aeolicus transfer-messenger RNA: structural and functional studies. J Mol Biol 2003; 331:457-71. [PMID: 12888352 DOI: 10.1016/s0022-2836(03)00760-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Transfer-messenger RNA (tmRNA, 10Sa RNA or ssrA) acts to rescue stalled bacterial ribosomes while encoding a peptide tag added trans-translationally to the nascent peptide, targeting it for proteolysis. The understanding at molecular level of this ubiquitous quality control system in eubacteria requires structural information. Here, we describe the purification and structural analysis of a functional fragment of both Aquifex aeolicus and Escherichia coli tmRNA, recapitulating their tRNA-like domain, which were expressed in vivo from synthetic genes. Both recombinant RNA are correctly processed at both 5' and 3' ends and are produced in quantities suitable for structural analysis by NMR and/or X-ray crystallography. The sequence and solution structure of the tRNA-like domains were analysed by various methods including structural mapping with chemical and enzymatic probes and 2D NMR spectroscopy. The minimalist RNAs contain two post-transcriptional base modifications, 5-methyluridine and pseudouridine, as the full-length tmRNA. Both RNAs fold into three stems, a D-analogue, a T-loop and a GAAA tetra-loop. 2D NMR analysis of the imino proton resonances of both RNAs allowed the assignment of the three stems and of a number of tertiary interactions. It shows the existence of interactions between the TPsiC-loop and the D-analogue, exhibiting a number of similarities and also differences with the canonical tRNA fold, indicating that RNA tertiary interactions can be modulated according to the sequence and secondary structure contexts. Furthermore, the E.coli minimalist RNA is aminoacylatable with alanine with a catalytic efficiency an order of magnitude higher than that for full-length tmRNA.
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Affiliation(s)
- Cyril Gaudin
- Laboratoire de Biochimie Pharmaceutique UPRES JE2311, Faculté de Pharmacie, Université de Rennes I, 2 avenue du Pr. Léon Bernard, 35043, Rennes, France
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52
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Khandogin J, Musier-Forsyth K, York DM. Insights into the regioselectivity and RNA-binding affinity of HIV-1 nucleocapsid protein from linear-scaling quantum methods. J Mol Biol 2003; 330:993-1004. [PMID: 12860122 DOI: 10.1016/s0022-2836(03)00658-2] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Human immunodeficiency virus type 1 (HIV-1) nucleocapsid protein (NC) plays several important roles in the viral life-cycle and presents an attractive target for rational drug design. Here, the macromolecular reactivity of NC and its binding to RNA is characterized through determination of electrostatic and chemical descriptors derived from linear-scaling quantum calculations in solution. The computational results offer a rationale for the experimentally observed susceptibility of the Cys49 thiolate toward small-molecule electrophilic agents, and support the recently proposed stepwise protonation mechanism of the C-terminal Zn-coordination complex. The distinctive binding mode of NC to SL2 and SL3 stem-loops of the HIV-1 genomic RNA packaging signal is studied on the basis of protein side-chain contributions to the electrostatic binding energies. These results indicate the importance of several basic residues in the 3(10) helical region and the N-terminal zinc finger, and rationalize the presence of several evolutionarily conserved residues in NC. The combined reactivity and RNA-binding study provides new insights that may contribute toward the structure-based design of anti-HIV therapies.
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Affiliation(s)
- Jana Khandogin
- Department of Chemistry, University of Minnesota, Minneapolis, MN 55455, USA
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53
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Tisné C, Roques BP, Dardel F. Specific recognition of primer tRNA Lys 3 by HIV-1 nucleocapsid protein: involvement of the zinc fingers and the N-terminal basic extension. Biochimie 2003; 85:557-61. [PMID: 12763315 DOI: 10.1016/s0300-9084(03)00034-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Reverse transcription of HIV-1 viral RNA uses human tRNA(Lys)(3) as a primer. We have previously characterised the structural aspects of the tRNA(Lys)(3) interaction by NMR. In HIV-1 virions, the nucleocapsid protein NCp7 contains two zinc fingers flanked by basic residues. Using NMR, the respective role of the N-terminal residues and the zinc fingers in the interaction with tRNA(Lys)(3)/NCp7 was investigated by studying the tRNA(Lys)(3) and tRNA(Lys)(3)/NCp7 complexes. The N-terminal basic residues do not change the footprint of NC on tRNA(Lys)(3)/Cys(23)NCp7 but strengthen the binding whereas the mutation of the zinc-binding histidine at position 23 that was shown to result in non-infectious particles prevents the interaction with the first bases of the acceptor stem.
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Affiliation(s)
- Carine Tisné
- Laboratoire de Cristallographie et RMN Biologiques, UMR 8015 CNRS, Faculté de Pharmacie, 4, avenue de l'Observatoire, 75006 Paris, France.
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54
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Beltz H, Azoulay J, Bernacchi S, Clamme JP, Ficheux D, Roques B, Darlix JL, Mély Y. Impact of the terminal bulges of HIV-1 cTAR DNA on its stability and the destabilizing activity of the nucleocapsid protein NCp7. J Mol Biol 2003; 328:95-108. [PMID: 12684000 DOI: 10.1016/s0022-2836(03)00244-4] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Reverse transcription of HIV-1 genomic RNA to double-stranded DNA by reverse transcriptase (RT) is a critical step in HIV-1 replication. This process relies on two viral proteins, the RT enzyme and nucleocapsid protein NCp7 that has well documented nucleic acid chaperone properties. At the beginning of the linear DNA synthesis, the newly made minus-strand strong-stop DNA ((-)ssDNA) is transferred to the 3'end of the genomic RNA by means of an hybridization reaction between transactivation response element (TAR) RNA and cTAR DNA sequences. Since both TAR sequences exhibit stable hairpin structures, NCp7 needs to destabilize the TAR structures in order to chaperone their hybridization. To further characterize the relationships between TAR stability and NC-mediated destabilization, the role of the A(49) and G(52) bulged residues in cTAR DNA stability was investigated. The stability of cTAR and mutants where one or the two terminal bulges were replaced by base-pairs as well as the NCp7-mediated destabilization of these cTAR sequences were examined. Thermodynamic data indicate that the two bulges cooperatively destabilize cTAR by reducing the stacking interactions between the bases. This causes a free energy change of about 6.4 kcal/mol and seems to be critical for NC activity. Time-resolved fluorescence data of doubly labelled cTAR derivatives suggest that NC-mediated melting of cTAR ends propagates up to the 10C.A(44) mismatch or T(40) bulge. Fluorescence correlation spectroscopy using two-photon excitation was also used to monitor cTAR ends fraying by NC. Results show that NC causes a very significant increase of cTAR ends fraying, probably limited to the terminal base-pair in the case of cTAR mutants. Since the TAR RNA and cTAR DNA bulges or mismatches appear well conserved among all HIV-1 strains, the present data support the notion of a co-evolutionary relationship between TAR and NC activity.
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Affiliation(s)
- Hervé Beltz
- Laboratoire de Pharmacologie et Physico-Chimie des Interactions Cellulaires et Moléculaires, UMR 7034 CNRS, Faculté de Pharmacie, Université Louis Pasteur, Strasbourg 1, 74, Route du Rhin, 67401 Illkirch Cedex, France
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55
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Azoulay J, Clamme JP, Darlix JL, Roques BP, Mély Y. Destabilization of the HIV-1 complementary sequence of TAR by the nucleocapsid protein through activation of conformational fluctuations. J Mol Biol 2003; 326:691-700. [PMID: 12581633 DOI: 10.1016/s0022-2836(02)01430-4] [Citation(s) in RCA: 99] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The nucleocapsid protein NCp7 of HIV-1 possesses nucleic acid chaperone properties that are critical for the two obligatory strand transfer reactions required for the synthesis of a complete proviral DNA by reverse transcriptase. The first DNA strand transfer relies on the destabilization by NCp7 of double-stranded segments of the transactivation response region (TAR) sequence at the 3' end of the genomic RNA and the complementary sequence cTAR at the 3' terminus of minus strong-stop DNA, the early product of reverse transcription. In order to determine the dynamics of NCp7-mediated nucleic acid destabilization, we investigated by time-resolved fluorescence spectroscopy and two photon fluorescence correlation spectroscopy, the interaction of a doubly labeled cTAR sequence with NC(12-55) containing NCp7 CCHC zinc fingers and flanking basic amino acid residues. From the chemical rates and the activation energy associated with the conformational fluctuations observed in the absence of NC, it is concluded that such fluctuations are associated with the opening and closing of the double-stranded terminal segments of cTAR. The destabilizing activity of NC(12-55) occurs mainly through a major increase of the opening rate constant of cTAR. Moreover, NC appears to augment the number of pathways between the open and closed states of cTAR, suggesting that it initiates melting of base-pairs at different locations within the terminal segments of cTAR. This activity of NC on the dynamics of cTAR secondary structure is thought to be critical for the formation of the cTAR-TAR complex, which is essential for the specificity and extent of proviral DNA synthesis by reverse transcriptase.
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Affiliation(s)
- Joel Azoulay
- Laboratoire de Pharmacologie et Physico-Chimie des Interactions Cellulaires et Moléculaires, UMR 7034 CNRS, Faculté de Pharmacie, 74, Route du Rhin, 67401 Illkirch, France
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56
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Hong MK, Harbron EJ, O'Connor DB, Guo J, Barbara PF, Levin JG, Musier-Forsyth K. Nucleic acid conformational changes essential for HIV-1 nucleocapsid protein-mediated inhibition of self-priming in minus-strand transfer. J Mol Biol 2003; 325:1-10. [PMID: 12473448 DOI: 10.1016/s0022-2836(02)01177-4] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Reverse transcription of the HIV-1 genome is a complex multi-step process. HIV-1 nucleocapsid protein (NC) is a nucleic acid chaperone protein that has been shown to greatly facilitate the nucleic acid rearrangements that precede the minus-strand transfer step in reverse transcription. NC destabilizes the highly structured transactivation response region (TAR) present in the R region of the RNA genome, as well as a complementary hairpin structure ("TAR DNA") at the 3'-end of the newly synthesized minus-strand strong-stop DNA ((-) SSDNA). Melting of the latter structure inhibits a self-priming (SP) reaction that competes with the strand transfer reaction. In an in vitro minus-strand transfer system consisting of a (-) SSDNA mimic and a TAR-containing acceptor RNA molecule, we find that when both nucleic acids are present, NC facilitates formation of the transfer product and the SP reaction is greatly reduced. In contrast, in the absence of the acceptor RNA, NC has only a small inhibitory effect on the SP reaction. To further investigate NC-mediated inhibition of SP, we developed a FRET-based assay that allows us to directly monitor conformational changes in the TAR DNA structure upon NC binding. Although the majority ( approximately 71%) of the TAR DNA molecules assume a folded hairpin conformation in the absence of NC, two minor "semi-folded" and "unfolded" populations are also observed. Upon NC binding to the TAR DNA alone, we observe a modest shift in the population towards the less-folded states. In the presence of the RNA acceptor molecule, NC binding to TAR DNA results in a shift of the majority of molecules to the unfolded state. These measurements help to explain why acceptor RNA is required for significant inhibition of the SP reaction by NC, and support the hypothesis that NC-mediated annealing of nucleic acids is a concerted process wherein the unwinding step occurs in synchrony with hybridization.
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Affiliation(s)
- Minh K Hong
- Department of Chemistry, University of Minnesota, 207 Pleasant Street S.E., Minneapolis, MN 55455-0431, USA
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57
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Bernacchi S, Stoylov S, Piémont E, Ficheux D, Roques BP, Darlix JL, Mély Y. HIV-1 nucleocapsid protein activates transient melting of least stable parts of the secondary structure of TAR and its complementary sequence. J Mol Biol 2002; 317:385-99. [PMID: 11922672 DOI: 10.1006/jmbi.2002.5429] [Citation(s) in RCA: 119] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The nucleocapsid protein NCp7 of HIV-1 possesses a nucleic acid chaperone activity that is critical in minus and plus strand transfer during reverse transcription. The minus strand transfer notably relies on the ability of NCp7 to destabilize the stable stem with five contiguous, double-stranded segments of both the TAR sequence at the 3' end of the viral genome and the complementary sequence, cTAR, in minus strong-stop DNA. In order to examine the nature and the extent of NCp7 destabilizing activity, we investigated, by absorbance and fluorescence spectroscopy, the interaction of TAR and cTAR with a (12-55)NCp7 peptide containing the zinc-finger motifs but lacking the ability to aggregate the oligonucleotides. The absorbance changes in the UV band of cTAR show that seven to eight base-pairs, on average, are melted per oligonucleotide at a ratio of one peptide to 7.5 nucleotides. In contrast, the melting of TAR does not exceed an average of one base-pair per oligonucleotide. This may be linked to the greater stability of TAR, since a strong correlation between NCp7 destabilizing effect and oligonucleotide stability was observed. The effect of (12-55)NCp7 on the stem terminus was investigated by using a cTAR molecule doubly labeled at the 3' and 5' ends by a donor/acceptor couple. In the absence of the peptide, about 80 % of the oligonucleotides are in a dark non-fluorescent state, having a close proximity of the two dyes. The remaining 20 % are distributed between three fluorescent species, having either the terminal segment, the two terminal segments or all segments of the stem melted. This is in line with a fraying mechanism wherein the stem terminus fluctuates rapidly between open and closed states. Addition of (12-55)NCp7 shifts the equilibrium toward the open species, suggesting that NC enhances fraying of the stem terminus. Taken together, our data suggest that NCp7 activates the transient opening of base-pairs in the least stable parts of the stem. Also, this activity of NCp7 was found to be dependent on the zinc-finger motifs, since no melting was observed with a fingerless NCp7 peptide.
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MESH Headings
- Base Pairing
- Base Sequence
- Capsid/chemistry
- Capsid/metabolism
- Capsid Proteins
- Crystallography, X-Ray
- Gene Products, gag/chemistry
- Gene Products, gag/metabolism
- HIV Long Terminal Repeat/genetics
- HIV-1/genetics
- Models, Molecular
- Molecular Sequence Data
- Nucleic Acid Conformation
- RNA, Viral/chemistry
- RNA, Viral/genetics
- RNA, Viral/metabolism
- RNA-Binding Proteins/chemistry
- RNA-Binding Proteins/metabolism
- Sequence Alignment
- Spectrometry, Fluorescence
- Spectrophotometry, Ultraviolet
- Structure-Activity Relationship
- Viral Proteins
- Zinc Fingers
- gag Gene Products, Human Immunodeficiency Virus
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Affiliation(s)
- Serena Bernacchi
- Laboratoire de Pharmacologie et Physico-Chimie des Interactions Cellulaires et Moléculaires, UMR 7034 CNRS, Faculté de Pharmacie, Université Louis Pasteur, 74, Route du Rhin, Strasbourg 1, 67401, France
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58
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Hargittai MR, Mangla AT, Gorelick RJ, Musier-Forsyth K. HIV-1 nucleocapsid protein zinc finger structures induce tRNA(Lys,3) structural changes but are not critical for primer/template annealing. J Mol Biol 2001; 312:985-97. [PMID: 11580244 DOI: 10.1006/jmbi.2001.5021] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Retroviral reverse transcriptases use host cellular tRNAs as primers to initiate reverse transcription. In the case of human immunodeficiency virus type 1 (HIV-1), the 3' 18 nucleotides of human tRNA(Lys,3) are annealed to a complementary sequence on the RNA genome known as the primer binding site (PBS). The HIV-1 nucleocapsid protein (NC) facilitates this annealing. To understand the structural changes that are induced upon NC binding to the tRNA alone, we employed a chemical probing method using the lanthanide metal terbium. At low concentrations of NC, the strong terbium cleavage observed in the core region of the tRNA is significantly attenuated. Thus, NC binding first results in disruption of the tRNA's metal binding pockets, including those that stabilize the D-TPsiC tertiary interaction. When NC concentrations approach the amount needed for complete primer/template annealing, NC further destabilizes the tRNA acceptor-TPsiC stem minihelix, as evidenced by increased terbium cleavage in this domain. A mutant form of NC (SSHS NC), which lacks the zinc finger structures, is able to anneal tRNA(Lys,3) efficiently to the PBS, and to destabilize the tRNA tertiary core, albeit less effectively than wild-type NC. This mutant form of NC does not affect cleavage significantly in the helical regions, even when bound at high concentrations. These results, as well as experiments conducted in the presence of polyLys, suggest that in the absence of the zinc finger structures, NC acts as a polycation, neutralizing the highly negative phosphodiester backbone. The presence of an effective multivalent cationic peptide is sufficient for efficient tRNA primer annealing to the PBS.
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Affiliation(s)
- M R Hargittai
- Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
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