CTIP2 is a negative regulator of P-TEFb.

The positive transcription elongation factor b (P-TEFb) is involved in physiological and pathological events including inflammation, cancer, AIDS, and cardiac hypertrophy. The balance between its active and inactive form is tightly controlled to ensure cellular integrity. We report that the transcriptional repressor CTIP2 is a major modulator of P-TEFb activity. CTIP2 copurifies and interacts with an inactive P-TEFb complex containing the 7SK snRNA and HEXIM1. CTIP2 associates directly with HEXIM1 and, via the loop 2 of the 7SK snRNA, with P-TEFb. In this nucleoprotein complex, CTIP2 significantly represses the Cdk9 kinase activity of P-TEFb. Accordingly, we show that CTIP2 inhibits large sets of P-TEFb- and 7SK snRNA-sensitive genes. In hearts of hypertrophic cardiomyopathic mice, CTIP2 controls P-TEFb-sensitive pathways involved in the establishment of this pathology. Overexpression of the ß-myosin heavy chain protein contributes to the pathological cardiac wall thickening. The inactive P-TEFb complex associates with CTIP2 at the MYH7 gene promoter to repress its activity. Taken together, our results strongly suggest that CTIP2 controls P-TEFb function in physiological and pathological conditions.

Activation of neutrophils by the two-component leukotoxin LukE/D from Staphylococcus aureus: proteomic analysis of the secretions.

Staphylococcus aureus is responsible for severe bacterial infections in hospitals and healthcare facilities. It produces single and bicomponent toxins (leukotoxins and hemolysins) that hinder innate immune function. Leukotoxin subunits bind to leukocyte cell membrane thus inducing transmembrane pores and subsequently, cell lysis. Leukotoxin LukE/D is a member of the bicomponent toxin family, but to date, no study concerning its involvement in host-pathogen interactions has been reported. In the present study, we performed the proteomic analysis of the secretions recovered after activation of human neutrophils by leukotoxin LukE/D. The neutrophil secretions were purified by RP-HPLC and different fractions were analyzed by Edman sequencing, LC-MS/MS, immunoblotted for chromogranin-derived peptides and further analyzed for antimicrobial properties. Proteomic analysis revealed that neutrophil secretions constitute a large number of proteins related with immune boosting mechanisms, proteolytic degradation, inflammatory process and antioxidant reactions.

Interplay between the HTLV-2 Tax and APH-2 proteins in the regulation of the AP-1 pathway.

BACKGROUND: In contrast with human T-cell leukemia virus type 1 (HTLV-1) that causes ATL (adult T-cell leukemia), HTLV-2 has not been causally linked to malignant disease. The minus strand of the HTLV genomes encode the regulatory proteins HTLV-1 bZIP factor (HBZ) for HTLV-1 and antisense protein of HTLV-2 (APH-2) for HTLV-2. Unlike the viral proteins Tax1 and Tax2, both HBZ and APH-2 are constitutively expressed in infected cells suggesting that they may play important roles in the pathogenesis of these viruses. To date, very little is known about the function of APH-2 except that it inhibits Tax2-mediated transcription of HTLV-2 genes. In the present study, we investigated the role of APH-2 in basal and Tax2B-mediated activation of the AP-1 pathway. RESULTS: We demonstrate that, unlike HBZ, APH-2 stimulates basal AP-1 transcription by interacting with c-Jun and JunB through its non-conventional bZIP domain. In addition, when Tax2 and APH-2 are co-expressed, they physically interact in vivo and in vitro and APH-2 acts as an inhibitor of Tax2-mediated activation of AP-1 transcription. CONCLUSIONS: This report is the first to document that HTLV-2 can modulate the AP-1 pathway. Altogether our results reveal that, in contrast with HBZ, APH-2 regulates AP-1 activity in a Tax2-dependant manner. As the AP-1 pathway is involved in numerous cellular functions susceptible to affect the life cycle of the virus, these distinct biological properties between HBZ and APH-2 may contribute to the differential pathogenic potential of HTLV-1 and HTLV-2.

[Molecular basis of HIV-1 latency - part I: physiology of HIV-1 latency]. / Un virus tapi dans l'ombre : les bases moléculaires de la latence du VIH-1 - Partie I : la physiologie de la latence du VIH-1.

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.

[Molecular basis of HIV-1 latency - Part II: HIV-1 reactivation and therapeutic implications]. / Un virus tapi dans l'ombre : les bases moléculaires de la latence du VIH-1 - Partie II : la réactivation de la latence du VIH-1 et ses implications thérapeutiques.

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.

Cross-company evaluation of the human lymphocyte activation assay.

Nonclinical immunotoxicity evaluation is an important component of safety assessment for pharmaceuticals. One in vitro assay that can be applied in a weight of evidence assessment is the human lymphocyte activation (HuLA) assay, an antigen recall assay, similar in many respects to the in vivo T-cell-dependent antibody response (TDAR) in that cooperation of multiple immune cell types are needed to produce responses. This assay uses human cells and is more amenable than the TDAR to compound ranking and mechanistic studies. The HuLA assay requires less time and drug than TDAR assays, uses a relevant antigen (influenza), reflects a human immune response, and applies principles of the 3Rs to non-clinical safety assessment. Peripheral blood mononuclear cells (PBMC) from flu-immunized donors are re-stimulated with flu-vaccine in the presence of test articles, and proliferation is measured. Published data demonstrate the applicability of the HuLA assay, but it has not been evaluated for reproducibility across testing sites. To evaluate assay reproducibility, scientists from a consortium of institutions conducted the assay in parallel, using a common pool of donor PBMC, influenza vaccine, and known immunosuppressant compounds (cyclosporine A and mycophenolic acid). The HuLA assay was highly reproducible in identification of inhibition of antigen-specific responses, and there was significant agreement across testing sites in the half maximal inhibitory concentration (IC50) values. Intra-site variability was the largest contributor to the variability observed within the assay. The HuLA assay was demonstrated to be ideally suited to comparing multiple compounds (i.e. compound ranking or benchmarking) within the same assay. Overall, the data reported herein support the HuLA assay as a useful tool in mechanistic evaluations of antigen-specific immune responses.

In Trauma Patients, the Occurrence of Early-Onset Nosocomial Infections is Associated With Increased Plasma Concentrations of Chromogranin A.

In previously healthy persons suffering from acute illnesses, nosocomial infections (NIs) are frequent. Their prevalence suggests the existence of as yet unknown conditions that may promote care-related infection. This study assessed whether the measurement of plasma chromogranin A, a stress-related protein involved in innate defense, is related to NI risk, and whether any chromogranin A-derived fragment included in vasostatin-I displays immunosuppressive activities related to AP-1 or NF-kappa B downregulation. At the clinical level, trauma patients and healthy controls were recruited to be eligible. Clinical histories were recorded, and standard biological tests (including plasma chromogranin A) were performed. For 9 randomly chosen patients and 16 controls, the time-dependent concentrations of chromogranin A (CGA) were assessed twice a day over 66 h. The data show that trauma patients present a higher value of CGA concentration during 66 h in comparison with healthy controls. In addition, patients maintaining this significant increase in CGA readily develop NIs. We therefore studied the effects of chromogranin A-derived peptides on monocytes, focusing on transcription factors that play a central role in inflammation. In vitro assay demonstrated that a chromogranin A-derived fragment (CGA47-70) displays a significant inhibition of NF-kappa B and AP-1 transcriptional activities in these cells. In conclusion, the occurrence of NI in trauma patients is associated with significantly increased plasma CGA concentrations. Downregulation of the two transcription factors by CGA47-70 might induce early acquired immune defect after a serious medical stress.

D-Cateslytin: a new antifungal agent for the treatment of oral Candida albicans associated infections.

The excessive use of antifungal agents, compounded by the shortage of new drugs being introduced into the market, is causing the accumulation of multi-resistance phenotypes in many fungal strains. Consequently, new alternative molecules to conventional antifungal agents are urgently needed to prevent the emergence of fungal resistance. In this context, Cateslytin (Ctl), a natural peptide derived from the processing of Chromogranin A, has already been described as an effective antimicrobial agent against several pathogens including Candida albicans. In the present study, we compared the antimicrobial activity of two conformations of Ctl, L-Ctl and D-Ctl against Candida albicans. Our results show that both D-Ctl and L-Ctl were potent and safe antifungal agents. However, in contrast to L-Ctl, D-Ctl was not degraded by proteases secreted by Candida albicans and was also stable in saliva. Using video microscopy, we also demonstrated that D-Ctl can rapidly enter C. albicans, but is unable to spread within a yeast colony unless from a mother cell to a daughter cell during cellular division. Besides, we revealed that the antifungal activity of D-Ctl could be synergized by voriconazole, an antifungal of reference in the treatment of Candida albicans related infections. In conclusion, D-Ctl can be considered as an effective, safe and stable antifungal and could be used alone or in a combination therapy with voriconazole to treat Candida albicans related diseases including oral candidosis.

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 Hp1alpha, 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.

On the way to find a cure: Purging latent HIV-1 reservoirs.

Introduction of cART in 1996 has drastically increased the life expectancy of people living with HIV-1. However, this treatment has not allowed cure as cessation of cART is associated with a rapid viral rebound. The main barrier to the eradication of the virus is related to the persistence of latent HIV reservoirs. Evidence is now accumulating that purging the HIV-1 reservoir might lead to a cure or a remission. The most studied strategy is the so called "shock and kill" therapy. This strategy is based on reactivation of dormant viruses from the latently-infected reservoirs (the shock) followed by the eradication of the reservoirs (the kill). This review focuses mainly on the recent advances made in the "shock and kill" therapy. We believe that a cure or a remission will come from combinatorial approaches i.e. combination of drugs to reactivate the dormant virus from all the reservoirs including the one located in sanctuaries, and combination of strategies boosting the immune system. Alternative strategies based on cell and gene therapy or based in inducing deep latency, which are evoked in this review reinforce the idea that at least a remission is attainable.

Repression of Human T-lymphotropic virus type 1 Long Terminal Repeat sense transcription by Sp1 recruitment to novel Sp1 binding sites.

Human T-lymphotropic Virus type 1 (HTLV-1) infection is characterized by viral latency in the majority of infected cells and by the absence of viremia. These features are thought to be due to the repression of viral sense transcription in vivo. Here, our in silico analysis of the HTLV-1 Long Terminal Repeat (LTR) promoter nucleotide sequence revealed, in addition to the four Sp1 binding sites previously identified, the presence of two additional potential Sp1 sites within the R region. We demonstrated that the Sp1 and Sp3 transcription factors bound in vitro to these two sites and compared the binding affinity for Sp1 of all six different HTLV-1 Sp1 sites. By chromatin immunoprecipitation experiments, we showed Sp1 recruitment in vivo to the newly identified Sp1 sites. We demonstrated in the nucleosomal context of an episomal reporter vector that the Sp1 sites interfered with both the sense and antisense LTR promoter activities. Interestingly, the Sp1 sites exhibited together a repressor effect on the LTR sense transcriptional activity but had no effect on the LTR antisense activity. Thus, our results demonstrate the presence of two new functional Sp1 binding sites in the HTLV-1 LTR, which act as negative cis-regulatory elements of sense viral transcription.

D-Cateslytin, a new antimicrobial peptide with therapeutic potential.

The rise of antimicrobial resistant microorganisms constitutes an increasingly serious threat to global public health. As a consequence, the efficacy of conventional antimicrobials is rapidly declining, threatening the ability of healthcare professionals to cure common infections. Over the last two decades host defense peptides have been identified as an attractive source of new antimicrobials. In the present study, we characterized the antibacterial and mechanistic properties of D-Cateslytin (D-Ctl), a new epipeptide derived from L-Cateslytin, where all L-amino acids were replaced by D-amino acids. We demonstrated that D-Ctl emerges as a potent, safe and robust peptide antimicrobial with undetectable susceptibility to resistance. Using Escherichia coli as a model, we reveal that D-Ctl targets the bacterial cell wall leading to the permeabilization of the membrane and the death of the bacteria. Overall, D-Ctl offers many assets that make it an attractive candidate for the biopharmaceutical development of new antimicrobials either as a single therapy or as a combination therapy as D-Ctl also has the remarkable property to potentiate several antimicrobials of reference such as cefotaxime, amoxicillin and methicillin.

Improving combination antiretroviral therapy by targeting HIV-1 gene transcription.

INTRODUCTION: Combination Antiretroviral Therapy (cART) has not allowed the cure of HIV. The main obstacle to HIV eradication is the existence of quiescent reservoirs. Several other limitations of cART have been described, such as strict life-long treatment and high costs, restricting it to Western countries, as well as the development of multidrug resistance. Given these limitations and the impetus to find a cure, the development of new treatments is necessary. Areas covered: In this review, we discuss the current status of several efficient molecules able to suppress HIV gene transcription, including NF-kB and Tat inhibitors. We also assess the potential of new proteins belonging to the intriguing DING family, which have been reported to have potential anti-HIV-1 activity by inhibiting HIV gene transcription. Expert opinion: Targeting HIV-1 gene transcription is an alternative approach, which could overcome cART-related issues, such as the emergence of multidrug resistance. Improving cART will rely on the identification and characterization of new actors inhibiting HIV-1 transcription. Combining such efforts with the use of new technologies, the development of new models for preclinical studies, and improvement in drug delivery will considerably reduce drug toxicity and thus increase patient adherence.

Targeting the Brain Reservoirs: Toward an HIV Cure.

One of the top research priorities of the international AIDS society by the action "Towards an HIV Cure" is the purge or the decrease of the pool of all latently infected cells. This strategy is based on reactivation of latently reservoirs (the shock) followed by an intensifying combination antiretroviral therapy (cART) to kill them (the kill). The central nervous system (CNS) has potential latently infected cells, i.e., perivascular macrophages, microglial cells, and astrocytes that will need to be eliminated. However, the CNS has several characteristics that may preclude the achievement of a cure. In this review, we discuss several limitations to the eradication of brain reservoirs and how we could circumvent these limitations by making it efforts in four directions: (i) designing efficient latency-reversal agents for CNS-cell types, (ii) improving cART by targeting HIV transcription, (iii) improving delivery of HIV drugs in the CNS and in the CNS-cell types, and (iv) developing therapeutic immunization. As a prerequisite to these efforts, we also believe that a better comprehension of molecular mechanisms involved in establishment and persistence of HIV latency in brain reservoirs are essential to design new molecules for strategies aiming to achieve a cure for instance the "shock and kill" strategy.

HIC1 controls cellular- and HIV-1- gene transcription via interactions with CTIP2 and HMGA1.

Among many cellular transcriptional regulators, Bcl11b/CTIP2 and HGMA1 have been described to control the establishment and the persistence of HIV-1 latency in microglial cells, the main viral reservoir in the brain. In this present work, we identify and characterize a transcription factor i.e. HIC1, which physically interacts with both Bcl11b/CTIP2 and HMGA1 to co-regulate specific subsets of cellular genes and the viral HIV-1 gene. Our results suggest that HIC1 represses Tat dependent HIV-1 transcription. Interestingly, this repression of Tat function is linked to HIC1 K314 acetylation status and to SIRT1 deacetylase activity. Finally, we show that HIC1 interacts and cooperates with HGMA1 to regulate Tat dependent HIV-1 transcription. Our results also suggest that HIC1 repression of Tat function happens in a TAR dependent manner and that this TAR element may serve as HIC1 reservoir at the viral promoter to facilitate HIC1/TAT interaction.

Regulation of HIV-1 gene transcription: from lymphocytes to microglial cells.

Transcription is a crucial step for human immunodeficiency virus type 1 (HIV-1) expression in all infected host cells, from T lymphocytes, thymocytes, monocytes, macrophages, and dendritic cells in the immune system up to microglial cells in the central nervous system. To maximize its replication, HIV-1 adapts transcription of its integrated proviral genome by ideally exploiting the specific cellular environment and by forcing cellular stimulatory events and impairing transcriptional inhibition. Multiple cell type-specific interplays between cellular and viral factors perform the challenge for the virus to leave latency and actively replicate in a great diversity of cells, despite the variability of its long terminal repeat region in different HIV strains. Knowledge about the molecular mechanisms underlying transcriptional regulatory events helps in the search for therapeutic agents that target the step of transcription in anti-HIV strategies.

Chromofungin, CgA47-66-derived peptide, produces basal cardiac effects and postconditioning cardioprotective action during ischemia/reperfusion injury.

Endogenous chromogranin A (CgA)-derived peptides are secreted by nervous, endocrine and immune cells. Chromofungin (Chr: CgA47-66) is one of these peptides that display antimicrobial activities and activate neutrophils, with important implications in inflammation and innate immunity. The aim of the present study is to examine the effects of Chr on isolated and Langendorff perfused rat hearts. The study was performed by using the isolated and Langendorff perfused rat hearts, Elisa assay and real-time PCR. We found that, under basal conditions, increasing doses (11-165nM) of Chr induced negative inotropic effects without changing coronary pressure. This action was mediated by the AKT/eNOS/cGMP/PKG pathway. We also found that Chr acted as a postconditioning (PostC) agent against ischemia/reperfusion (I/R) damages, reducing infarct size and LDH level. Cardioprotection involved PI3K, RISK pathway, MitoKATP and miRNA-21. We suggest that Chr directly affects heart performance, protects against I/R myocardial injuries through the activation of prosurvival kinases. Results may propose Chr as a new physiological neuroendocrine modulator able to prevent heart dysfunctions, also encouraging the clarification of its clinical potential.

Cateslytin, a chromogranin A derived peptide is active against Staphylococcus aureus and resistant to degradation by its proteases.

Innate immunity involving antimicrobial peptides represents an integrated and highly effective system of molecular and cellular mechanisms that protects host against infections. One of the most frequent hospital-acquired pathogens, Staphylococcus aureus, capable of producing proteolytic enzymes, which can degrade the host defence agents and tissue components. Numerous antimicrobial peptides derived from chromogranins, are secreted by nervous, endocrine and immune cells during stress conditions. These kill microorganisms by their lytic effect at micromolar range, using a pore-forming mechanism against Gram-positive bacteria, filamentous fungi and yeasts. In this study, we tested antimicrobial activity of chromogranin A-derived peptides (catestatin and cateslytin) against S. aureus and analysed S. aureus-mediated proteolysis of these peptides using HPLC, sequencing and MALDI-TOF mass spectrometry. Interestingly, this study is the first to demonstrate that cateslytin, the active domain of catestatin, is active against S. aureus and is interestingly resistant to degradation by S. aureus proteases.

Genome-wide binding map of the HIV-1 Tat protein to the human genome.

The HIV-1 Trans-Activator of Transcription (Tat) protein binds to multiple host cellular factors and greatly enhances the level of transcription of the HIV genome. While Tat's control of viral transcription is well-studied, much less is known about the interaction of Tat with the human genome. Here, we report the genome-wide binding map of Tat to the human genome in Jurkat T cells using chromatin immunoprecipitation combined with next-generation sequencing. Surprisingly, we found that ~53% of the Tat target regions are within DNA repeat elements, greater than half of which are Alu sequences. The remaining target regions are located in introns and distal intergenic regions; only ~7% of Tat-bound regions are near transcription start sites (TSS) at gene promoters. Interestingly, Tat binds to promoters of genes that, in Jurkat cells, are bound by the ETS1 transcription factor, the CBP histone acetyltransferase and/or are enriched for histone H3 lysine 4 tri-methylation (H3K4me3) and H3K27me3. Tat binding is associated with genes enriched with functions in T cell biology and immune response. Our data reveal that Tat's interaction with the host genome is more extensive than previously thought, with potentially important implications for the viral life cycle.