COUP-TF interacting protein 2 represses the initial phase of HIV-1 gene transcription in human microglial cells

Human immunodeficiency virus type 1 (HIV-1) gene transcription is characterized by two temporally distinct phases. While the initial phase relies solely on cellular transcription factors, the subsequent phase is activated by the viral Tat transactivator. We have previously reported that the subsequent phase of viral gene transcription can be repressed by the chicken ovalbumin upstream promoter transcription factor (COUP-TF)-interacting protein 2 (CTIP2) in human microglial cells [O. Rohr, D. Lecestre, S. Chasserot-Golaz, C. Marban, D. Avram, D. Aunis, M. Leid and E. Schaeffer (2003), J. Virol., 77, 5415–5427]. Here, we demonstrate that CTIP proteins also repress the initial phase of HIV-1 gene transcription, mainly supported by the cellular transcription factors Sp1 and COUP-TF in microglial cells. We report that CTIP2 represses Sp1- and COUP-TF-mediated activation of HIV-1 gene transcription and viral replication as a result of physical interactions with COUP-TF and Sp1 in microglial nuclei. Using laser confocal microscopy CTIP2 was found to colocalize with Sp1, COUP-TF and the heterochromatin-associated protein Hp1α, which is mainly detected in transcriptionally repressed heterochromatic region. Moreover, we describe that CTIP2 can be recruited to the HIV-1 promoter via its association with Sp1 bound to the GC-box sequences of the long terminal repeat (LTR). Since our findings demonstrate that CTIP2 interacts with the HIV-1 proximal promoter, it is likely that CTIP2 promotes HIV-1 gene silencing by forcing transcriptionally repressed heterochromatic environment to the viral LTR region

How to maintain the transcriptional post-integrative latency,implications of CTIP2 and LSD1Titre en anglais

L'expression du VIH-1 est contrôlée par de nombreux phénomènes très complexes. Une étude de notre laboratoire a pu montrer l'importance du cofacteur transcriptionnel CTIP2 dans le maintien de la latence du VIH-1 dans les cellules microgliales. En effet, CTIP2 recrute un complexe enzymatique comprenant HDAC1 et 2 et SUV39H1, afin de condenser la chromatine qui sera alors transcriptionnellement inactive. Dans un premier temps, j ai mis en évidence l'effet répresseur de LSD1 sur la transcription virale dans les cellules microgliales. J ai également pu démontrer que le recrutement de LSD1 sur le promoteur viral est associé à hSET1, une histone méthyltransférase, induisant alors la triméthylation de la lysine 4 de l'histone H3. J ai pu également mettre en lumière que le recrutement de LSD1 est nécessaire à l'association de CTIP2 au promoteur viral. Ainsi, CTIP2 et LSD1 coopèrent dans la répression de la transcription virale dans les cellules microgliales. Dans la seconde partie de ma thèse, j ai étudié l'influence du cofacteur transcriptionnel CTIP2 sur la transcription virale dans les lymphocytes T CD4+. CTIP2 facilite la transactivation médiée par Tat. Dans ce cadre, ainsi que suite à une activation de la transcription par le PMA, CTIP2 est recruté sur le promoteur viral de manière concomitante avec HDAC2, SUV39H1 et HP1g. Ici, le recrutement de ces enzymes ne conduit pas à la formation d'un environnement hétérochromatinien mais à l'activation de la transcription virale. Ainsi, mes travaux ont pu mettre en évidence la dualité de CTIP2 qui est un répresseur du VIH-1 dans les cellules microgliales infectées de manière latente et un activateur du VIH-1 dans les lymphocytes T CD4+ infectés de manière productive.HIV-1 expression is controlled by various and complex phenomenons. We have shown that CTIP2 contributes to the post-integrative latency in microglial cells. CTIP2 associates with HDAC1, HDAC2 and SUV39H1 to favour heterochromatic environment surrounding the HIV promoter, thereby silencing HIV-1 expression. I first described that the histone demethylase LSD1 represses HIV-1 transcription in microglial cells. LSD1 is associated with the HIV-1 promoter and facilitates the recruitment of the histone methylase hSET1 which is responsible for the Histone H3 Lysine 4 trimethylation. Moreover, my studies indicate that LSD1 is required in order to recruit CTIP2 onto the HIV-1 promoter. Thus, LSD1 and CTIP2 cooperate physically and functionally to induce a transcriptional repression. In the second part of my thesis, I investigated the influence of CTIP2 on HIV-1 transcription in the T CD4+ lymphocytes. Following Tat expression or PMA treatment, CTIP2 enhances the Tat-mediated transactivation. CTIP2 induces the recruitment of HDAC2, SUV39H1 and HP1g on the HIV-1 promoter. Here, the recruitment of these enzymes does not lead to the formation of a heterochromatic environment but to the activation of the viral expression. So, my works were able to bring to light the duality of CTIP2 which repress the HIV-1 transcription in latently infected microglial cells and facilitates the HIV-1 expression in productively infected CD4+ T cells

How to maintain the transcriptional post-integrative latency,implications of CTIP2 and LSD1Titre en anglais

L'expression du VIH-1 est contrôlée par de nombreux phénomènes très complexes. Une étude de notre laboratoire a pu montrer l'importance du cofacteur transcriptionnel CTIP2 dans le maintien de la latence du VIH-1 dans les cellules microgliales. En effet, CHIV-1 expression is controlled by various and complex phenomenons. We have shown that CTIP2 contributes to the post-integrative latency in microglial cells. CTIP2 associates with HDAC1, HDAC2 and SUV39H1 to favour heterochromatic environment surrounding

How to maintain the transcriptional post-integrative latency : implications of CTIP2 and LSD1

L’expression du VIH-1 est contrôlée par de nombreux phénomènes très complexes. Une étude de notre laboratoire a pu montrer l’importance du cofacteur transcriptionnel CTIP2 dans le maintien de la latence du VIH-1 dans les cellules microgliales. En effet, CTIP2 recrute un complexe enzymatique comprenant HDAC1 et 2 et SUV39H1, afin de condenser la chromatine qui sera alors transcriptionnellement inactive. Dans un premier temps, j’ai mis en évidence l’effet répresseur de LSD1 sur la transcription virale dans les cellules microgliales. J’ai également pu démontrer que le recrutement de LSD1 sur le promoteur viral est associé à hSET1, une histone méthyltransférase, induisant alors la triméthylation de la lysine 4 de l’histone H3. J’ai pu également mettre en lumière que le recrutement de LSD1 est nécessaire à l’association de CTIP2 au promoteur viral. Ainsi, CTIP2 et LSD1 coopèrent dans la répression de la transcription virale dans les cellules microgliales. Dans la seconde partie de ma thèse, j’ai étudié l’influence du cofacteur transcriptionnel CTIP2 sur la transcription virale dans les lymphocytes T CD4+. CTIP2 facilite la transactivation médiée par Tat. Dans ce cadre, ainsi que suite à une activation de la transcription par le PMA, CTIP2 est recruté sur le promoteur viral de manière concomitante avec HDAC2, SUV39H1 et HP1γ. Ici, le recrutement de ces enzymes ne conduit pas à la formation d’un environnement hétérochromatinien mais à l’activation de la transcription virale. Ainsi, mes travaux ont pu mettre en évidence la dualité de CTIP2 qui est un répresseur du VIH-1 dans les cellules microgliales infectées de manière latente et un activateur du VIH-1 dans les lymphocytes T CD4+ infectés de manière productive.HIV-1 expression is controlled by various and complex phenomenons. We have shown that CTIP2 contributes to the post-integrative latency in microglial cells. CTIP2 associates with HDAC1, HDAC2 and SUV39H1 to favour heterochromatic environment surrounding the HIV promoter, thereby silencing HIV-1 expression. I first described that the histone demethylase LSD1 represses HIV-1 transcription in microglial cells. LSD1 is associated with the HIV-1 promoter and facilitates the recruitment of the histone methylase hSET1 which is responsible for the Histone H3 Lysine 4 trimethylation. Moreover, my studies indicate that LSD1 is required in order to recruit CTIP2 onto the HIV-1 promoter. Thus, LSD1 and CTIP2 cooperate physically and functionally to induce a transcriptional repression. In the second part of my thesis, I investigated the influence of CTIP2 on HIV-1 transcription in the T CD4+ lymphocytes. Following Tat expression or PMA treatment, CTIP2 enhances the Tat-mediated transactivation. CTIP2 induces the recruitment of HDAC2, SUV39H1 and HP1γ on the HIV-1 promoter. Here, the recruitment of these enzymes does not lead to the formation of a heterochromatic environment but to the activation of the viral expression. So, my works were able to bring to light the duality of CTIP2 which repress the HIV-1 transcription in latently infected microglial cells and facilitates the HIV-1 expression in productively infected CD4+ T cells

Molecular basis of HIV-1 latency - Part II: HIV-1 reactivation and therapeutic implications

The latent HIV-1 reservoirs established early during infection present a major obstacle for virus eradication. Complete eradication of the virus from infected patients may require a purge of the reservoirs. Since the development of a HIV-1 vaccine is not achieved, and therefore remains a major challenge for the immunologists, future direction towards an effective curative therapy for HIV-1 infection will rely on the development of original therapeutic strategies which take into account latency, chronic replication and accessibility to tissue-sanctuary

Molecular basis of HIV-1 latency - part I: physiology of HIV-1 latency

The introduction of the highly active antiretroviral therapy (HAART) in 1996 has greatly extended survival and raised hopes for the eradication of HIV-1. Unfortunately, the optimism declined by revealing the existence of latent HIV-1 reservoirs in cells targeted by the virus. The long-lived HIV-1 reservoirs constitute a major obstacle to the eradication of HIV-1. Understanding the molecular mechanisms of virus latency is essential for efficient therapeutic intervention against the virus

Inhibition of HIV-1 expression by CTIP2-mediated recruitment of HDAC activities to the Long Terminal Repeat.

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CTIP2 colocalizes with Sp1 and COUP-TF within Hp1α-associated structures

<p><b>Copyright information:</b></p><p>Taken from "COUP-TF interacting protein 2 represses the initial phase of HIV-1 gene transcription in human microglial cells"</p><p>Nucleic Acids Research 2005;33(7):2318-2331.</p><p>Published online 22 Apr 2005</p><p>PMCID:PMC1084325.</p><p>© The Author 2005. Published by Oxford University Press. All rights reserved</p> () Microglial cells were transfected or not with Flag-CTIP2 as indicated. After being treated, endogenous Sp1, COUP-TF and Hp1α proteins were immunodetected with primary anti-COUP-TF (Santa Cruz Biotechnology) (images 1 and 2), anti-Sp1 (images 6 and 7) and anti-Hp1α antibodies (images 11 and 12). Overexpressed Flag-CTIP2 was detected with antibodies directed against the Flag epitope (images 3, 8 and 13). The primary immunocomplexes were revealed by CY2- or CY3-labeled anti-species secondary antibodies (green or red staining). Mask column (images 5, 10 and 15) shows the colocalized CY2 and CY3 stainings. () Microglial cells expressing RFP-CTIP2 (image 1) and GFP-Sp1 (image 3) were subjected to endogenous COUP-TF immunodetection with anti-COUP-TF antibodies (kindly provided by J. E. Mertz). COUP-TF immunocomplexes were stained by CY5- (blue staining) labeled anti-species secondary antibodies (image 2). Pattern of RFP-CTIP2 and GFP-Sp1 expressed alone are presented on images 5 and 6, respectively. ( and ) Coverslips were subjected to confocal microscopy analysis. Bar, 10 μm