Post-translational modifications in DNA topoisomerase 2α highlight the role of a eukaryote-specific residue in the ATPase domain

Type 2 DNA topoisomerases (Top2) are critical components of key protein complexes involved in DNA replication, chromosome condensation and segregation, as well as gene transcription. The Top2 were found to be the main targets of anticancer agents, leading to intensive efforts to understand their functional and physiological role as well as their molecular structure. Post-translational modifications have been reported to influence Top2 enzyme activities in particular those of the mammalian Top2α isoform. In this study, we identified phosphorylation, and for the first time, acetylation sites in the human Top2α isoform produced in eukaryotic expression systems. Structural analysis revealed that acetylation sites are clustered on the catalytic domains of the homodimer while phosphorylation sites are located in the C-terminal domain responsible for nuclear localization. Biochemical analysis of the eukaryotic-specific K168 residue in the ATPase domain shows that acetylation affects a key position regulating ATP hydrolysis through the modulation of dimerization. Our findings suggest that acetylation of specific sites involved in the allosteric regulation of human Top2 may provide a mechanism for modulation of its catalytic activity.Facultad de Ciencias ExactasInstituto de Física de Líquidos y Sistemas Biológico

Post-translational modifications in DNA topoisomerase 2α highlight the role of a eukaryote-specific residue in the ATPase domain

Type 2 DNA topoisomerases (Top2) are critical components of key protein complexes involved in DNA replication, chromosome condensation and segregation, as well as gene transcription. The Top2 were found to be the main targets of anticancer agents, leading to intensive efforts to understand their functional and physiological role as well as their molecular structure. Post-translational modifications have been reported to influence Top2 enzyme activities in particular those of the mammalian Top2α isoform. In this study, we identified phosphorylation, and for the first time, acetylation sites in the human Top2α isoform produced in eukaryotic expression systems. Structural analysis revealed that acetylation sites are clustered on the catalytic domains of the homodimer while phosphorylation sites are located in the C-terminal domain responsible for nuclear localization. Biochemical analysis of the eukaryotic-specific K168 residue in the ATPase domain shows that acetylation affects a key position regulating ATP hydrolysis through the modulation of dimerization. Our findings suggest that acetylation of specific sites involved in the allosteric regulation of human Top2 may provide a mechanism for modulation of its catalytic activity.Fil: Bedez, Claire. Université de Strasbourg; FranciaFil: Lotz, Christophe. Université de Strasbourg; FranciaFil: Batisse, Claire. Université de Strasbourg; FranciaFil: Broeck, Arnaud Vanden. Université de Strasbourg; FranciaFil: Stote, Roland H.. Université de Strasbourg; FranciaFil: Howard, Eduardo Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; ArgentinaFil: Pradeau-Aubreton, Karine. Université de Strasbourg; FranciaFil: Ruff, Marc. Université de Strasbourg; FranciaFil: Lamour, Valérie. Université de Strasbourg; Franci

Réactivation de l'herpèsvirus humain de type 6 (HHV-6) (outils de détection et mécanismes moléculaires)

L'herpèsvirus humain de type 6 (HHV-6) est un virus très répandu qui reste dans l'organisme sous une forme latente après la primo-infection. Cette latence virale est entrecoupée d'épisodes de réactivation, s'accompagnant d'une production de nombreuses particules infectieuses. La réactivation semble anodine chez le sujet sain, mais peut être très grave dans différents contextes d'immunodépression, notamment après transplantation, A l'heure actuelle, les mécanismes permettant le maintien de la latence ou à l'inverse ceux entraînant la réactivation sont inconnus. L'objectif de ce travail de thèse était double. Dans un premier temps, des outils moléculaires permettant la détection de la multiplication d'HHV-6 ont été développés. Pour cela une technique de quantification par PCR en temps réel a été mise au point. De même la détection des ARNm du virus associés à sa réplication par une RT-PCR a été réalisée. Afin de tester ces outils de détection dans un contexte de réactivation, elles ont été appliquées à des prélèvements sanguins de patients transplantés. Les deux méthodes se sont alors révélées efficace pour mettre en évidence la réactivation d'HHV-6. Puis dans un deuxième temps, l'effet de l'expression du facteur de transcription NF- B sur la transcription des gènes très précoces du virus a été recherché. Pour cela, un super-répresseur de NF- B (I BaMut) a été transfecté dans des cellules favorables à la croissance virale. En inhibant la voie canique de signalisation de NF- B, une diminution de la réplication du virus, mise en évidence par une baisse de la transcription des ARNm viraux à l'aide d'une technique de RT-PCR quantitative et par une réduction du nombre de cellules en immunofluorescence, a été observée. Un rôle important du facteur de transcription NF- B dans la multiplication du virus HHV-6 a ainsi été démontréLIMOGES-BU Sciences (870852109) / SudocSudocFranceF

Successful Treatment of Human Herpesvirus 6 Encephalomyelitis in Immunocompetent Patient

We report the case of human herpesvirus 6 (HHV-6) encephalomyelitis in an immunocompetent patient, which was confirmed by viral amplification from cerebrospinal fluid. Cidofovir was used followed by ganciclovir because of an adverse effect to probenecid. The patient recovered. HHV-6 should be recognized as one of the causes of encephalomyelitis

Production of unstable proteins through the formation of stable core complexes

International audiencePurification of proteins that participate in large transient complexes is impeded by low amounts, heterogeneity, instability and poor solubility. To circumvent these difficulties we set up a methodology that enables the production of stable complexes for structural and functional studies. This procedure is benchmarked and applied to two challenging protein families: the human steroid nuclear receptors (SNR) and the HIV-1 pre-integration complex. In the context of transcriptional regulation studies, we produce and characterize the ligand-binding domains of the glucocorticoid nuclear receptor and the oestrogen receptor beta in complex with a TIF2 (transcriptional intermediary factor 2) domain containing the three SNR-binding motifs. In the context of retroviral integration, we demonstrate the stabilization of the HIV-1 integrase by formation of complexes with partner proteins and DNA. This procedure provides a powerful research tool for structural and functional studies of proteins participating in non-covalent macromolecular complexes

The HIV-1 Pre-Integration Complexes: Structures, Functions and Dynamics

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Efficient production of protein complexes in mammalian cells using a poxvirus vector

Abstract Background: The production of full length, biologically active proteins in mammalian cells is critical for a wide variety of purposes ranging from structural studies to preparation of subunit vaccines. Prior research has shown that Modified vaccinia virus Ankara encoding the bacteriophage T7 RNA polymerase (MVA-T7) is particularly suitable for high level expression of proteins upon infection of mammalian cells. The expression system is safe for users and 10-50 mg of full length, biologically active proteins may be obtained in their native state, from a few litres of infected cell cultures. Results: Here we report further improvements which allow an increase in the ease and speed of recombinant virus isolation, the scale-up of protein production and the simultaneous synthesis of several polypeptides belonging to a protein complex using a single virus vector. Isolation of MVA-T7 viruses encoding foreign proteins was simplified by combining positive selection for virus recombinants and negative selection against parental virus, a process which eliminated the need for tedious plaque purification. Scale-up of protein production was achieved by infecting a BHK 21 suspension cell line and inducing protein expression with previously infected cells instead of virus, thus saving time and effort in handling virus stocks. Protein complexes were produced from infected cells by concatenating the Tobacco Etch Virus (TEV) N1A protease sequence with each of the genes of the complex into a single ORF, each gene being separated from the other by twin TEV protease cleavage sites. We report the application of these methods to the production of a complex formed on the one hand between the HIV-1 integrase and its cell partner LEDGF and on the other between the HIV-1 VIF protein and its cell partners APOBEC3G, CBFβ, Elo B and Elo C. Conclusions: The strategies developed in this study should be valuable for the overexpression and subsequent purification of numerous protein complexes

Unstable Protein Purification Through the Formation of Stable Complexes

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