[show abstract][hide abstract] ABSTRACT: A series of 2-hydroxy-1,3-dioxoisoquinoline-4-carboxamides featuring an N-hydroxyimide chelating functionality was evaluated for their inhibitory properties against human immunodeficiency virus type 1 integrase (HIV-1 IN). Several derivatives displayed low nanomolar IC50 values comparable to that of the clinically used raltegravir. A marked effect of one compound on both primary IN-catalyzed reactions, strand transfer (ST), and 3′ processing (3′-P), emphasizes a novel IN inhibition mechanism establishing it as a potential new generation IN inhibitor. Substitution of the 2-hydroxyisoquinoline-1,3- dione scaffold at position 4 by carboxamido chains was beneficial for antiviral activity since reproducible low micromolar anti- HIV activities were obtained for the first time within this scaffold.
[show abstract][hide abstract] ABSTRACT: Higher eukaryotic organisms have a variety of specific and nonspecific defense mechanisms against viral invaders. In animal cells, viral replication may be limited through the decrease in translation. Some viruses, however, have evolved mechanisms that counteract the response of the host. We report that infection by HIV-1 triggers acute decrease in translation. The human protein kinase GCN2 (eIF2AK4) is activated by phosphorylation upon HIV-1 infection in the hours following infection. Thus, infection by HIV-1 constitutes a stress that leads to the activation of GCN2 with a resulting decrease in protein synthesis. We have shown that GCN2 interacts with HIV-1 integrase (IN). Transfection of IN in amino acid-starved cells, where GCN2 is activated, increases the protein synthesis level. These results point to an as yet unknown role of GCN2 as an early mediator in the cellular response to HIV-1 infection, and suggest that the virus is able to overcome the involvement of GCN2 in the cellular response by eliciting methods to maintain protein synthesis.
Cellular and Molecular Life Sciences CMLS 02/2013; · 5.62 Impact Factor
[show abstract][hide abstract] ABSTRACT: Polynucleotidyl transferases are enzymes involved in several DNA mobility mechanisms in prokaryotes and eukaryotes. Some of them such as retroviral integrases are crucial for pathogenous processes and are therefore good candidates for therapeutic approaches. To identify new therapeutic compounds and new tools for investigating the common functional features of these proteins, we addressed the inhibition properties of natural stilbenoids deriving from resveratrol on two models: the HIV-1 integrase and the eukaryote MOS-1 transposase. Two resveratrol dimers, leachianol F and G, were isolated for the first time in Vitis along with fourteen known stilbenoids: E-resveratrol, E-piceid, E-pterostilbene, E-piceatannol, (+)-E-ε-viniferin, E-ε-viniferinglucoside, E-scirpusin A, quadragularin A, ampelopsin A, pallidol, E-miyabenol C, E-vitisin B, hopeaphenol, and isohopeaphenol and were purified from stalks of Vitis vinifera (Vitaceae), and moracin M from stem bark of Milliciaexelsa (Moraceae). These compounds were tested in in vitro and in vivo assays reproducing the activity of both enzymes. Several molecules presented significant inhibition on both systems. Some of the molecules were found to be active against both proteins while others were specific for one of the two models. Comparison of the differential effects of the molecules suggested that the compounds could target specific intermediate nucleocomplexes of the reactions. Additionally E-pterostilbene was found active on the early lentiviral replication steps in lentiviruses transduced cells. Consequently, in addition to representing new original lead compounds for further modelling of new active agents against HIV-1 integrase, these molecules could be good tools for identifying such reaction intermediates in DNA mobility processes.
PLoS ONE 01/2013; 8(11):e81184. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: In contrast to canonical proteases, total immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies (Abs) from HIV-infected patients hydrolyze effectively only HIV integrase (IN), reverse transcriptase (RT), human casein, and serum albumin. Anti-IN IgG and IgM isolated by chromatography on IN-Sepharose hydrolyze specifically only IN but not many other tested proteins. Total Abs from HIV-infected patients hydrolyze not only globular proteins but also different specific and nonspecific tri-, tetra-, and 20- to 25-mer oligopeptides (OPs) with a higher rate than anti-IN Abs isolated using IN-Sepharose. A similar situation was observed for IgG from patients with multiple sclerosis and HIV-infected patients, which after purification on myelin basic protein (MBP)-Sepharose and RT-Sepharose specifically hydrolyze only MBP and RT, respectively. The active sites of all anti-protein abzymes are localized on their light chains, whereas the heavy chain is responsible for the affinity of protein substrates. Interactions of intact globular proteins with both light and heavy chains of abzymes provide the specificity of protein hydrolysis. The affinity of anti-IN and anti-MBP abzymes for intact IN and MBP is approximately 10(2)- to 10(5)-fold higher than for short and long specific and nonspecific OPs. The data suggest that all OPs interact mainly with the light chain of different Abs, which possesses a lower affinity for substrates, and therefore, depending on the OP sequences, their hydrolysis may be less specific or completely nonspecific. The data indicate that the relative activity of Abs not fractionated on specific protein sorbents in the hydrolysis of specific and nonspecific OPs can correspond to an average proteolytic activity of light chains of polyclonal Abs directed against many different proteins.
Journal of Molecular Recognition 04/2012; 25(4):193-207. · 3.01 Impact Factor
[show abstract][hide abstract] ABSTRACT: Stable HIV-1 replication requires the DNA repair of the integration locus catalyzed by cellular factors. The human RAD51 (hRAD51) protein plays a major role in homologous recombination (HR) DNA repair and was previously shown to interact with HIV-1 integrase (IN) and inhibit its activity. Here we determined the molecular mechanism of inhibition of IN. Our standard in vitro integration assays performed under various conditions promoting or inhibiting hRAD51 activity demonstrated that the formation of an active hRAD51 nucleofilament is required for optimal inhibition involving an IN-DNA complex dissociation mechanism. Furthermore we show that this inhibition mechanism can be promoted in HIV-1-infected cells by chemical stimulation of the endogenous hRAD51 protein. This hRAD51 stimulation induced both an enhancement of the endogenous DNA repair process and the inhibition of the integration step. Elucidation of this molecular mechanism leading to the restriction of viral proliferation paves the way to a new concept of antiretroviral therapy based on the enhancement of endogenous hRAD51 recombination activity and highlights the functional interaction between HIV-1 IN and hRAD51.
Journal of Virology 01/2012; 86(1):513-26. · 5.08 Impact Factor
[show abstract][hide abstract] ABSTRACT: HIV-1 integrase (IN) catalyzes integration of a DNA copy of the viral genome into the host genome. In contrast to canonical proteases (trypsin, chymotrypsin and proteinase K), IgGs and IgMs isolated from HIV-infected patients by affinity chromatography on immobilized IN specifically hydrolyzed only IN but not many other tested intact globular proteins. The sites of IN cleavage determined by MALDI mass spectrometry were localized mainly within seven known immunodominant regions of IN. Thin layer chromatography analysis has shown that the abzymes (Abzs) could also cleave 17 to 22-mer oligopeptides (OPs) corresponding to the immunodominant regions of IN sequence with a much higher rate than non-specific long peptides or three- and tetrapeptides of various sequence. Therefore, a prolonged incubation of IN with AIDS IgGs and IgMs having high catalytic activity usually produces many OPs of different length. Since anti-IN IgGs and IgMs can efficiently hydrolyze IN, a positive role of the Abzs in counteracting the infection is possible.
International Immunology 08/2011; 23(10):601-12. · 3.14 Impact Factor
[show abstract][hide abstract] ABSTRACT: The HIV-1 integrase (IN) mutations Y143C/R are known as raltegravir (RAL) primary resistance mutations. In a previous study (S. Reigadas et al., PLoS One 5:e10311, 2010), we investigated the genetic pathway and the dynamics of emergence of the Y143C/R mutations in three patients failing RAL-containing regimens. In these patients, the Y143C/R mutation was associated with the T97A mutation. The aim of the present biochemical and molecular studies in vitro was to evaluate whether the secondary mutation, T97A, associated with the Y143C/R mutation could increase the level of resistance to RAL and impact IN activities. Site-directed mutagenesis experiments were performed with expression vectors harboring the region of the pol gene coding for IN. With a 3'-end processing assay, the 50% inhibitory concentrations (IC(50)) were 1.2 μM, 1.2 μM, 2.4 μM (fold change [FC], 2), and 20 μM (FC, 16.7) for IN wild type (WT), the IN T97A mutation, the IN Y143C/T97A mutation, and the IN Y143R/T97A mutation, respectively. FCs of 18 and 100 were observed with the strand transfer assay for IN Y143C/T97A and Y143R/T97A mutations, with IC(50) of 0.625 μM and 2.5 μM, respectively. In the strand transfer assay, the IN Y143C or R mutation combined with the secondary mutation T97A severely impaired susceptibility to RAL compared to results with the IN Y143C or R mutation alone. Assays without RAL suggested that the T97A mutation could rescue the catalytic activity which was impaired by the presence of the Y143C/R mutation. The combination of the T97A mutation with the primary RAL resistance mutations Y143C/R strongly reduces the susceptibility to RAL and rescues the catalytic defect due to the Y143C/R mutation. This result indicates that the emergence of the Y143C/R/T97A double-mutation pattern in patients is a signature of a high resistance level.
Antimicrobial Agents and Chemotherapy 07/2011; 55(7):3187-94. · 4.57 Impact Factor
[show abstract][hide abstract] ABSTRACT: 2-Hydroxyisoquinoline-1,3(2H,4H)-dione was recently discovered as a scaffold for the inhibition of HIV-1 integrase and the ribonuclease H function of HIV-1 reverse transcriptase. First, we investigate its interaction with Mg(2+) and Mn(2+) using different spectroscopic techniques and report that 2-hydroxyisoquinoline-1,3(2H,4H)-dione forms a 1:1 complex with Mg(2+) but a 1:2 complex with Mn(2+). The complex formation requires enolization of the ligand. ESR spectroscopy shows a redox reaction between the ligand and Mn(2+) producing superoxide anions. Second, 2-hydroxyisoquinoline-1,3(2H,4H)-dione, its magnesium complex, and its 4-methyl and 2-hydroxy-4-methoxycarbonylisoquinoline-1,3(2H,4H)-diones were tested as inhibitors of HIV-1 integrase, reverse transcriptase ribonuclease H, and DNA polymerase functions. Their antiviral activities were evaluated and 2-hydroxy-4-methoxycarbonyl-isoquinoline-1,3(2H,4H)-dione was found to inhibit the viral replication of HIV-1 in MT-4 cells. Cross-resistance was measured for this compound on three different viral strains. Experimental data suggest that the antiviral activity of 2-hydroxy-4-methoxycarbonylisoquinoline-1,3(2H,4H)-dione is probably due to the RNase H inhibition.
Journal of Medicinal Chemistry 03/2011; 54(6):1812-24. · 5.61 Impact Factor
[show abstract][hide abstract] ABSTRACT: We report herein the synthesis of a series of fifteen 2-hydroxyisoquinoline-1,3(2H,4H)-dione derivatives. Alkyl and arylalkyl groups were introduced on position 4 of the basis scaffold. All the compounds presented poor inhibitory properties against HIV-1 reverse transcriptase ribonuclease H (RNase H). Four compounds inhibited HIV-1 integrase at a low micromolar level. A docking study using the later crystallographic data available for PFV integrase allowed us to explain the slightly improved integrase inhibitory activities of 4-pentyl and 4-(3-phenylpropyl)-2-hydroxyisoquinoline-1,3(2H,4H)-diones, when compared to the basis scaffold. Physicochemical studies were consistent with 1:1 and 1:2 (metal/ligand) stoichiometries of the magnesium complexes in solution. Unfortunately all tested compounds exhibited high cellular cytotoxicity in cell culture which limited their applications as antiviral agents. However these identified integrase inhibitors provide a very good basis for the development of new hits.
European journal of medicinal chemistry 02/2011; 46(2):535-46. · 3.27 Impact Factor
[show abstract][hide abstract] ABSTRACT: Establishment of stable HIV-1 infection requires the efficient integration of the retroviral genome into the host DNA. The molecular mechanism underlying the control of this process by the chromatin structure has not yet been elucidated. We show here that stably associated nucleosomes strongly inhibit in vitro two viral-end integration by decreasing the accessibility of DNA to integrase. Remodeling of the chromatinized template by the SWI/SNF complex, whose INI1 major component interacts with IN, restores and redirects the full-site integration into the stable nucleosome region. These effects are not observed after remodeling by other human remodeling factors such as SNF2H or BRG1 lacking the integrase binding protein INI1. This suggests that the restoration process depends on the direct interaction between IN and the whole SWI/SNF complex, supporting a functional coupling between the remodeling and integration complexes. Furthermore, in silico comparison between more than 40,000 non-redundant cellular integration sites selected from literature and nucleosome occupancy predictions also supports that HIV-1 integration is promoted in the genomic region of weaker intrinsic nucleosome density in the infected cell. Our data indicate that some chromatin structures can be refractory for integration and that coupling between nucleosome remodeling and HIV-1 integration is required to overcome this natural barrier.
[show abstract][hide abstract] ABSTRACT: Human immunodeficiency virus type 1 integrase (IN) catalyzes integration of a DNA copy of the viral genome into the host genome. It was shown previously that IN preincubation with various oligodeoxynucleotides (ODNs) induces formation of dimers and oligomers of different gyration radii; only specific ODNs stimulate the formation of catalytically active dimers. Here we have shown that preincubation of IN with specific and nonspecific ODNs leads to a significant and comparable decrease in its hydrolysis by chymotrypsin, while nonspecific ODNs protect the enzyme from the hydrolysis by trypsin worse than specific ODNs; all ODNs had little effect on the IN hydrolysis by proteinase K. In contrast to canonical proteweases, IgGs from HIV-infected patients specifically hydrolyze only IN. While d(pT)(n) markedly decreased the IgG-dependent hydrolysis of IN, d(pA)(n) and d(pA)(n) •d(pT)(n) demonstrated no detectable protective effect. The best protection from the hydrolysis by IgGs was observed for specific single- and especially double-stranded ODNs. Although IN was considerably protected by specific ODNs, proteolytic IgGs and IgMs significantly suppressed both 3'-processing and integration reaction catalyzed by IN. Since anti-IN IgGs and IgMs can efficiently hydrolyze IN, a positive role of abzymes in counteracting the infection cannot be excluded.
Journal of Molecular Recognition 01/2011; 24(6):1067-76. · 3.01 Impact Factor
[show abstract][hide abstract] ABSTRACT: IgG abzymes (Abzs) with different catalytic activities are a distinctive feature of various autoimmune (AI) diseases. At the same time, data concerning IgMs with catalytic activities are very limited. Electrophoretically and immunologically homogeneous IgMs were isolated from the sera of acquired immunodeficiency syndrome (AIDS) patients by chromatography on several affinity sorbents. Several rigid criteria have been applied to show that the integrase (IN)-hydrolyzing activity is an intrinsic property of IgMs from HIV-infected patients but not from healthy donors. We present evidence showing that 22 of 24 (91.7%) IgMs purified from the sera of HIV-infected patients specifically hydrolyze only HIV IN but not many other tested proteins. Usually, proteolytic antibodies of AI patients are serine protease-like or metal dependent. Only 30% of IN-hydrolyzing IgMs were inhibited by specific inhibitors of serine proteases and 60% by inhibitors of metal-dependent proteases. Unusually, a significant reduction of the activity by specific inhibitors of acidic (in 20% of IgM preparations) and thiol proteases (in 100% of IgM preparations) was observed. Although HIV infection leads to formation of antibodies to many viral and human antigens, possible biological roles for most of them are unknown. Since anti-IN IgG can efficiently hydrolyze IN, a positive role of Abzs in counteracting the infection cannot be excluded. In addition, detection of IN-hydrolyzing activity can be useful for diagnostic purposes and for assessment of the immune status in AIDS patients.
International Immunology 08/2010; 22(8):671-80. · 3.14 Impact Factor
[show abstract][hide abstract] ABSTRACT: Resistance to HIV-1 integrase (IN) inhibitor raltegravir (RAL), is encoded by mutations in the IN region of the pol gene. The emergence of the N155H mutation was replaced by a pattern including the Y143R/C/H mutations in three patients with anti-HIV treatment failure. Cloning analysis of the IN gene showed an independent selection of the mutations at loci 155 and 143. Characterization of the phenotypic evolution showed that the switch from N155H to Y143C/R was linked to an increase in resistance to RAL. Wild-type (WT) IN and IN with mutations Y143C or Y143R were assayed in vitro in 3'end-processing, strand transfer and concerted integration assays. Activities of mutants were moderately impaired for 3'end-processing and severely affected for strand transfer. Concerted integration assay demonstrated a decrease in mutant activities using an uncleaved substrate. With 3'end-processing assay, IC(50) were 0.4 microM, 0.9 microM (FC = 2.25) and 1.2 microM (FC = 3) for WT, IN Y143C and IN Y143R, respectively. An FC of 2 was observed only for IN Y143R in the strand transfer assay. In concerted integration, integrases were less sensitive to RAL than in ST or 3'P but mutants were more resistant to RAL than WT.
PLoS ONE 01/2010; 5(4):e10311. · 3.73 Impact Factor
[show abstract][hide abstract] ABSTRACT: Autoantibodies with enzymic activities (abzymes) are a distinctive feature of autoimmune diseases. It was interesting whether Abs from patients with viral diseases can hydrolyze viral proteins. Electrophoretically and immunologically homogeneous IgGs were isolated from sera of AIDS patients by chromatography on several affinity sorbents. We present evidence showing that 89.5% IgGs purified from the sera of HIV-infected patients using several affinity resins including Sepharose with immobilized integrase specifically hydrolyze only HIV integrase (IN) but not many other tested proteins. Several rigid criteria have been applied to show that the IN-hydrolyzing activity is an intrinsic property of AIDS IgGs but not from healthy donors. Similar to autoimmune proteolytic abzymes, IN-hydrolyzing IgGs from some patients were inhibited by specific inhibitors of serine and metal-dependent proteases but a significant inhibition of the activity by specific inhibitors of acidic- and thiol-like proteases was observed for the first time. Although HIV infection leads to formation of Abs to many viral and human antigens, no possible biological role for most of them is known. Since anti-IN IgG can efficiently hydrolyze IN, a positive role of abzymes in counteracting the infection cannot be excluded. In addition, detection of IN-hydrolyzing activity can be useful for diagnostic purposes and for estimation of the immune status in AIDS patients.
[show abstract][hide abstract] ABSTRACT: Intracellular transport of karyophilic cargos comprises translocation to the nuclear envelope and subsequent nuclear import. Small cargos such as isolated proteins can reach the nuclear envelope by diffusion but movement of larger structures depends on active translocation, typically using microtubules. Centripetal transport ends at the perinuclear microtubule organizing centre called the spindle pole body (SPB) in yeast. Previously, we found by two hybrids that the karyophilic lentiviral-encoded integrase (IN) interacts with two yeast microtubule-associated proteins, Dyn2p (dynein light chain protein) and Stu2p, a centrosomal protein (de Soultrait et al., 2002). Thus, to investigate the hinge between cytoplasmic retrograde transport and nuclear import, we decided to analyse HIV-1 IN trafficking in yeast as the model, since each of these biological mechanisms is evolutionarily conserved in eukaryotic cells. Here, we found an accumulation of IN at the SPB in yeast via Stu2p colocalization. Disruption of the microtubule network by nocodazole or IN expression in a dynein 2-deficient yeast strain prevented IN accumulation in the nuclear periphery and additionally inhibited IN transport into the nucleus. By mutagenesis, we showed that trafficking of IN towards the SPB requires the C-terminus of the molecule. Taking our findings together, we proposed a model in which IN nuclear import seems to depend on an essential intermediate step in the SPB. We found that Dyn2p and Stu2p play an important role in driving IN toward MTOC and could optimize nuclear entry of the retroviral enzyme. Our results suggest a new hypothesis in keeping with the current HIV-1 intracellular trafficking model.
[show abstract][hide abstract] ABSTRACT: HIV-1 integrase (IN) oligomerization and DNA recognition are crucial steps for the subsequent events of the integration reaction. Recent advances described the involvement of stable intermediary complexes including dimers and tetramers in the in vitro integration processes, but the initial attachment events and IN positioning on viral ends are not clearly understood. In order to determine the role of the different IN oligomeric complexes in these early steps, we performed in vitro functional analysis comparing IN preparations having different oligomerization properties. We demonstrate that in vitro IN concerted integration activity on a long DNA substrate containing both specific viral and nonspecific DNA sequences is highly dependent on binding of preformed dimers to viral ends. In addition, we show that IN monomers bound to nonspecific DNA can also fold into functionally different oligomeric complexes displaying nonspecific double-strand DNA break activity in contrast to the well known single strand cut catalyzed by associated IN. Our results imply that the efficient formation of the active integration complex highly requires the early correct positioning of monomeric integrase or the direct binding of preformed dimers on the viral ends. Taken together the data indicates that IN oligomerization controls both the enzyme specificity and activity.
Nucleic Acids Research 12/2008; 36(22):7043-58. · 8.28 Impact Factor
[show abstract][hide abstract] ABSTRACT: We report herein the synthesis of a series of 19 2-hydroxyisoquinoline-1,3(2H,4H)-dione derivatives variously substituted at position 7 aimed at inhibiting selectively two-metal ion catalytic active sites. The compounds were tested against HIV-1 reverse transcriptase (RT) polymerase, HIV-1 RT ribonuclease H (RNase H), and HIV-1 integrase (IN). Most compounds displayed poor inhibition of RT polymerase even at 50 microM. The majority of the synthesized compounds inhibited RNase H and IN at micromolar concentrations, and some of them were weakly selective for IN. Surprisingly, two new hits were discovered, which displayed a high selectivity for IN with submicromolar IC50 values. These enzymatic inhibitory properties may be related to the metal binding abilities of the compounds. Physicochemical studies were consistent with a 1/1 stoichiometry of the magnesium complexes in solution, and the metal complexation was strictly dependent on the enolization abilities of the compounds. Unfortunately, all tested compounds exhibited high cellular cytotoxicity in cell culture which limits their applications as antiviral agents.
Journal of Medicinal Chemistry 12/2008; 51(24):7717-30. · 5.61 Impact Factor
[show abstract][hide abstract] ABSTRACT: HIV-1 integrase (IN) catalyses integration of a DNA copy of the viral genome into the host genome. Specific interactions between retroviral IN and long terminal repeats (LTR) are required for this insertion. To characterize quantitatively the influence of the determinants of DNA substrate specificity on the oligomerization status of IN, we used the small-angle X-ray scattering (SAXS) technique. Under certain conditions in the absence of ODNs IN existed only as monomers. IN preincubation with specific ODNs led mainly to formation of dimers, the relative amount of which correlated well with the increase in the enzyme activity in the 3'-processing reaction. Under these conditions, tetramers were scarce. Non-specific ODNs stimulated formation of catalytically inactive dimers and tetramers. Complexes of monomeric, dimeric and tetrameric forms of IN with specific and non-specific ODNs had varying radii of gyration (R(g)), suggesting that the specific sequence-dependent formation of IN tetramers can probably occur by dimerization of two dimers of different structure. From our data we can conclude that the DNA-induced oligomerization of HIV-1 IN is probably of importance to provide substrate specificity and to increase the enzyme activity.
Nucleic Acids Research 02/2007; 35(3):975-87. · 8.28 Impact Factor
[show abstract][hide abstract] ABSTRACT: HIV-1 integrase (IN) is the key enzyme catalyzing the proviral DNA integration step. Although the enzyme catalyzes the integration step accurately in vitro, whether IN is sufficient for in vivo integration and how it interacts with the cellular machinery remains unclear. We set up a yeast cellular integration system where integrase was expressed as the sole HIV-1 protein and targeted the chromosomes. In this simple eukaryotic model, integrase is necessary and sufficient for the insertion of a DNA containing viral LTRs into the genome, thereby allowing the study of the isolated integration step independently of other viral mechanisms. Furthermore, the yeast system was used to identify cellular mechanisms involved in the integration step and allowed us to show the role of homologous recombination systems. We demonstrated physical interactions between HIV-1 IN and RAD51 protein and showed that HIV-1 integrase activity could be inhibited both in the cell and in vitro by RAD51 protein. Our data allowed the identification of RAD51 as a novel in vitro IN cofactor able to down regulate the activity of this retroviral enzyme, thereby acting as a potential cellular restriction factor to HIV infection.
Nucleic Acids Research 02/2006; 34(21):6215-24. · 8.28 Impact Factor
[show abstract][hide abstract] ABSTRACT: The oligomeric state of active human immunodeficiency virus type 1 (HIV-1) integrase (IN) has not been clearly elucidated. We analyzed the activity of the different purified oligomeric forms of recombinant IN obtained after stabilization by platinum crosslinking. The crosslinked tetramer isolated by gel chromatography was able to catalyze the full-site integration of the two viral LTR ends into a target DNA in vitro, whereas the isolated dimeric form of the enzyme was involved in the processing and integration of only one viral end. Accurate concerted integration by IN tetramers was confirmed by cloning and sequencing. Kinetic studies of DNA-integrase complexes led us to propose a model explaining the formation of an active complex. Our data suggest that the tetrameric IN bound to the viral DNA ends is the minimal complex involved in the concerted integration of both LTRs and should be the oligomeric form targeted by future inhibitors.
Nucleic Acids Research 02/2005; 33(3):977-86. · 8.28 Impact Factor