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Arsenic trioxide, As 2O3, already used in human anti-cancer therapy, is also an efficient agent against the autoimmune and inflammatory diseases developed in MRL/lpr mice. Inflammatory bowel diseases (IBDs), notably Crohn’s disease, which remain without efficient treatment, display autoimmune and inflammatory components. We, therefore, hypothesized that As2O 3 may be active on IBDs. Using the 2,4,6-trinitrobenzene sulfonic acid-induced murine model of colitis, we demonstrate that As2O3 used either in a preventive or a curative mode markedly reduced the induced colitis as assessed by macroscopic and microscopic scores, leading to prolonged mice survival. In addition, As2O3 was able to inhibit NF-κB expression and DNA-binding in colon extracts leading to decreased cytokine gene expression (i.e. tumor necrosis factor-α, interleukin(IL)-1β, IL-12, IL-17, IL-18, and IL-23). Interestingly, As2O3 also reduced keratinocyte-derived chemokine (KC), inducible nitric oxide synthase (iNOS) mRNA levels, and myeloperoxidase (MPO) protein expression suggesting an impairment of neutrophils. This was associated with a marked increase of procaspase-3 and induced caspase-3 activation. This caspase-3 co-localized with MPO in the remaining neutrophils suggesting that As2O 3 might have eliminated inflamed cells probably by inducing their apoptosis. These results assessed the potent anti-inflammatory effect of As2O 3, that targets both NF-κB and caspase-3 pathways, and suggests a therapeutic potential for Crohn’s disease and other severe IBDs. [ABSTRACT FROM AUTHOR]

Type I interferon (IFN) enhances the transcription of the tumor suppressor gene p53. To elucidate the molecular mechanism mediating IFN-induced apoptosis, we analysed programmed cell death in response to type I (IFNa) or type II (IFN?) treatment in relation to p53 status. In two cell lines (MCF-7, SKNSH), IFNa, but not IFN?, enhanced apoptosis in a p53-dependent manner. Furthermore, only IFNaupregulated p53 as well as p53 target genes (Noxa, Mdm2 and CD95). The apoptotic response to IFNadecreased in the presence of ZB4, an anti-CD95 antibody, suggesting that CD95 is involved in this process. When p53 was inactivated by the E6 viral protein or the expression of a p53 mutant, IFNa-induced apoptosis and p53 target genes upregulation were abrogated. Altogether these results demonstrate that p53 plays a pivotal role in the IFNa-induced apoptotic response. IFNa-induced PML was unable to recruit p53 into nuclear bodies and its downregulation by siRNA did not alter CD95 expression. In contrast, IFN?-induced apoptosis is p53-independent. CD95 and IFN-regulatory factor 1 (IRF1) are directly upregulated by this cytokine. Apoptotic response to IFN?is decreased in the presence of ZB4 and strongly diminished by IRF1 siRNA, implicating both CD95 and IRF1 in IFN?-induced apoptotic response. Taken together, these results show that in two different cell lines, IFNaand IFN?, induce p53-dependent -independent apoptosis, respectively.Oncogene (2005) 24, 605-615. doi:10.1038/sj.onc.1208204 Published online 6 December 2004 [ABSTRACT FROM AUTHOR]

Arsenic trioxide (As2O3) can induce clinical remission in patients with acute promyelocytic leukemia (APL), including those who have relapsed after treatment with all-trans-retinoic acid (RA). In vitro studies with the APL-derived NB4 cell line showed that As2O3 exerts a dose-dependent dual effect, which induces apoptosis at 1?µM, whereas at a lower concentration of 0.1?µM, a partial differentiation of APL is observed. In non-APL cells, interferon (IFN) a and 1?µM As2O3 act synergistically to induce apoptosis. In this report, we show that in NB4 cells and in two RA-resistant NB4-derived cell lines, NB4-R1 and NB4-R2, IFNa or IFN? combined with 0.1?µM As2O3 lead to an increased maturation effect. Moreover, IFN? alone is able to differentiate RA-sensitive and -resistant cells with a higher maturation effect on NB4-R2 cells. In contrast, all these cells underwent apoptosis in the presence of the cytokine and a higher concentration of As2O3. IFN? boosted As2O3-induced apoptosis in APL cells as tested by TUNEL, Annexin V staining and activation of caspase 3. As2O3 differently altered IFN-induced gene products; it downregulated PML/RARa and PML, did not alter PKR and Stat1, and upregulated interferon regulatory family (IRF)-1. Synergism by IFN? and arsenic on IRF-1 expression is mediated by a composite element in the IRF-1 promoter that includes an IFN?-activation site (GAS) overlapped by a nonconsensus site for nuclear factor kappa B (NF?B). Arsenic has no effect on NF?B, whereas it enhances the activation of Stat1 by IFN? in NB4 cells leading to an increase in IRF-1 expression.Oncogene (2003) 22, 9121-9130. doi:10.1038/sj.onc.1207090 [ABSTRACT FROM AUTHOR]

Analysis of 16-S rRNA synthesized in Eseherichia coli D10 (met-) incubated in a medium containing ethionine in place of methionine shows that it lacks most and probably all of the methyl groups present in normal 16-S rRNA but possesses the same 3'-OH, and 5′-phosphate terminal sequences as the latter. 23-S rRNA formed in ethionine-treated cells also contains normal terminal sequences. 5-S rRNAs of normal and ethionine-treated E. coli D10 are identical. These results lead to the conclusion that methylation of ribosomal precursor RYAs is not necessary for their maturation to products with normal chain lengths and does not influence the conformation of 16-S rRNA.. [ABSTRACT FROM AUTHOR]

Small Ubiquitin-like MOdifier (SUMO) conjugation to proteins has essential roles in several processes including localization, stability, and function of several players implicated in intrinsic and innate immunity. In human, five paralogs of SUMO are known of which three are ubiquitously expressed (SUMO1, 2, and 3). Infection by rhabdoviruses triggers cellular responses through the activation of pattern recognition receptors, which leads to the production and secretion of interferon. This review will focus on the effects of the stable expression of the different SUMO paralogs or Ubc9 depletion on rhabdoviruses-induced interferon production and interferon signaling pathways as well as on the expression and functions of restriction factors conferring the resistance to rhabdoviruses. [ABSTRACT FROM AUTHOR]

Interferons (IFNs) orchestrate immune defense through induction of hundred of genes. Small ubiquitin-like modifier (SUMO) is involved in various cellular functions, but little is known about its role on IFN responses. Prior work identified SUMOylation of STAT1 as an important mode of regulation of IFN γ signaling. Here, we investigated the various roles of SUMO in IFN signaling, transcriptional response and IFN-induced biological effects. We first show that SUMO overexpression leads to STAT1 SUMOylation and to a decrease in IFN-induced STAT1 phosphorylation. This process correlates with lower levels of STAT1 binding to GAS in response to IFN γ , while the binding of an ISGF3-like complex to ISRE in response to IFN α is not altered. Interestingly, IFNs exert a negative retro-control on their own signaling by enhancing STAT1 SUMOylation. Furthermore, we show that expression of each SUMO paralog selectively inhibits IFN γ -induced IP-10 and TAP1 mRNA expression. Importantly, inhibition of IFN γ signaling by SUMO is associated with a decrease of IFN γ -induced apoptosis and cell growth inhibition as well as a dramatic reduction of IP-10-induced chemotaxis. Conversely, inhibition of SUMOylation results in a higher IFN γ -induced STAT1 phosphorylation and biological responses. In conclusion, our work thus allows the inclusion of SUMO to the list of negative regulators of IFN signaling known to date and posits SUMO as a possible contributor to IFN γ resistance. [ABSTRACT FROM AUTHOR]

SUMOylation is the post-translational covalent but reversible conjugation of SUMO to proteins. In human, the SUMO protein family consists of SUMO1 and two highly homologous proteins SUMO2 and SUMO3 (collectively called SUMO2/3), which cannot be distinguished by currently available antibodies. We have shown that SUMO overexpression leads to STAT1 SUMOylation and to a decrease in IFN-induced STAT1 phosphorylation resulting in an inhibition of IFN γ -induced transcription without affecting that of IFN α . Here, we focused on the IFN-induced gene products associated with PML nuclear bodies and we show that in SUMO3-expressing cells, neither IFN α nor IFN γ could increase PML and Sp100 protein expression, as they enhanced their SUMO3 conjugation and subsequent proteasomal degradation. Since it is known that SUMO3 is important for the recruitment of RNF4, a poly-SUMO-dependent E3 ubiquitin ligase implicated in PML degradation in arsenic-treated cells, we went on to show that RNF4 depletion in IFN-treated HeLa-SUMO3 cells prevented PML degradation, thus restoring an increase of PML and Sp100 protein expression in response to IFN. In addition, SUMO3, but not SUMO1, overexpression reduced the capacity of IFN to inhibit viral proteins and EMCV production. These results are consistent with the degradation of PML in IFN-treated HeLa-SUMO3 cells, and with our previous observation that PML depletion decreases the anti-EMCV effect of IFN (Maroui et al., J Virol 2011). Altogether, our results uncover a new role for SUMO3 in the modulation of both type I and type II IFN responses. [ABSTRACT FROM AUTHOR]

PML, also known as TRIM19, belongs to the family of tripartite motif (TRIM) proteins. Like some other TRIM proteins, PML exerts a broad antiviral activity. PML is mainly expressed in the nucleus, where it forms dynamic structures known as PML nuclear bodies that recruit many proteins, such as Sp100 and Daxx. It was reported that HIV-1 infection induces the translocation of PML from the nucleus to the cytoplasm (Turelli et al., 2001). This paper also suggested that PML could interfere with HIV-1 infection but this was later contradicted (Berthoux et al., 2003). We sought to re-evaluate the implication of PML during HIV-1 infection. We show that infection by HIV-1 but also other retroviruses triggers the formation of PML cytoplasmic bodies, as early as 30 min post-infection. PML re-localization was blocked by reverse-transcription inhibitors and was not observed following infection with unrelated viruses, suggesting it is specifically triggered by retroviral reverse-transcription. Furthermore, we show that PML interferes with an early step of retroviral infection since PML knockdown dramatically increases RT efficiency. However, the effect of PML on retroviral infection was found to be indirect and to operate through the stabilization of one of its well-characterized partners, Daxx. In the presence of PML, Daxx inhibits an early step of reverse-transcription thereby interfering with HIV-1 infection. Like PML, Daxx is an interferon-inducible protein that provides intrinsic immunity against various viruses. Our study unravels for the first time its capacity to inhibit an early step of HIV-1 replication. [ABSTRACT FROM AUTHOR]

PML/TRIM19 is the organizer of PML nuclear bodies (NB), a multiprotein complex associated to the nuclear matrix, which recruit a large number of proteins involved in various cellular processes. Alternative splicing from a single PML gene generates 6 nuclear PML isoforms (PMLI to PMLVI) and one cytoplasmic isoform, PMLVII. Murine PML-null primary cells are resistant to TGF-β-induced apoptosis. Cytoplasmic PML is an essential activator of TGF-β signaling by increasing the phosphorylation of transcription factors SMAD2/3 while nuclear PML plays a role in TGF-β-induced caspase 8 activation and apoptosis. TGF-β targets nuclear PML by inducing its conjugation to SUMO. In the nucleus, PML is mainly expressed in the nucleoplasm with a small fraction in the nuclear matrix. In response to TGF-β, PML and caspase 8 shift to the nuclear matrix, where both PML and caspase 8 colocalise within PML NBs. Here, we review the implication of cytoplasmic and nuclear PML isoforms in TGF-β response., (© 2020 médecine/sciences – Inserm.)

PML/TRIM19 is the organizer of PML nuclear bodies (NB), large multiprotein structures associated to the nuclear matrix, which recruit a great number of proteins and which are implicated in various cellular processes including antiviral defense. The conjugation of PML to SUMO is required for the formation and function of PML NB. Alternative splicing from a single PML gene generates several PML isoforms (PMLI to PMLVIIb), each harboring a specific carboxy-terminal region. This variability allows each isoform to recruit different partners and thus confers them specific functions. PML gene is directly induced by interferon and certain PML isoforms are implicated in its antiviral properties, as they display intrinsic antiviral activities against RNA or DNA viruses. One isoform, PMLIV, is also implicated in innate immunity by enhancing IFN-β production during a viral infection. Here we review recent findings on PML/TRIM19 implication in interferon response and antiviral defense, at the interface between intrinsic and innate immunity., (© 2014 médecine/sciences – Inserm.)

Since 1996, arsenic trioxide (As2O3) is used to treat patients with acute promyelocytic leukemia. We have recently shown that As2O3 is a novel promising therapeutic agent for the autoimmune diseases (human lupus-like syndrome) and the massive lymphoproliferation (human autoimmune lymphoproliferative-like syndrome) developed by MRL/lpr mice. As2O3 is able to achieve an almost complete regression of antibody- and cell-mediated manifestations in MRL/lpr mice. As2O3 eliminated the activated T lymphocytes responsible for lymphoproliferation and skin, lung, and kidney lesions. This treatment also markedly reduced anti-DNA autoantibodies, rheumatoid factor, IL-18, IFN-gamma, nitric oxide metabolites, TNF-alpha, Fas ligand and IL-10 levels, and immune-complex deposits in glomeruli, leading to significantly prolonged survival rates.

Cytokines, hormones or growth factors induce a variety of biological responses including proliferation, differentiation and apoptosis. After binding to their specific cell surface receptors, these stimuli induce the activation of a number of signaling pathways including the activation of JAK (JAnus Kinase) proteins by auto and transphosphorylation. Activated JAK phosphorylate the receptor chains on tyrosines, creating docking sites for cytoplasmic transcription factors named STAT (Signal Transducers and Activators of Transcription). Furthermore, the JAK phosphorylate the STAT which form dimers and migrate to the nucleus where they bind to specific DNA sequences leading to the activation of transcription. The multiplicity of JAK (4 members) and STAT (7 members) and their associations with multiple possible partners allow the formation of various STAT homo and heterodimers and STAT-containing transcriptional complexes. Each of these complexes lead to the specific regulation of gene transcription. Negative regulation of the JAK/STAT signaling pathway is crucial to switch off the cytokine/growth factors' signal. Three families of proteins : the phosphotyrosine phosphatases (SHPs, CD45, PTP1B/TC-PTP), the SOCS proteins (Suppressors Of Cytokine Signaling) and the PIAS (Protein Inhibitor of Activated STAT) are involved in this process. These proteins act at various levels of the JAK/STAT pathway. Thus, tyrosine-phosphatases dephosphorylate activated JAK, STAT or cytokine receptors. PIAS interact with activated STAT and inhibit their DNA binding or their transactivating capacity, probably in relation with their intrinsic SUMO E3-ligase activity. The tyrosine phosphatases and the PIAS are constitutively present in the cell and represent a first level of regulation. The SOCS, which represent a second level of JAK/STAT negative control, are induced by cytokines and exert a negative feed-back loop. Indeed, they interact with activated JAK or with phosphorylated receptors, inhibiting the recruitment of STAT, the activation of the JAK enzymatic activity, or inducing the proteasome-dependant degradation of activated JAK or receptors.

Lymphocytes from aged autoimmune MRL/lpr mice overexpress Fas ligand (FasL), and are cytotoxic against Fas+ target cells. This cytotoxic potential is only partly due to FasL, as wild-type MRL+/+ lymphocytes are not able to kill Fas+ targets after induction of FasL. In addition, serum levels of interferon-alpha (IFN-alpha) increase in parallel with the Fas-dependent cytotoxic potential of lymphocytes from MRL/lpr mice as they age. To understand the mechanisms underlying these observations, combined suppression subtractive hybridization (SSH) and RT-PCR were used to study differential gene expression in splenocytes from MRL/lpr mice compared with splenocytes from MRL+/+ mice. Twenty-two genes were upregulated transcriptionally in MRL/lpr splenocytes compared with their MRL+/+ counterparts. Furthermore, 9 of these genes were also upregulated after treatment of MRL/lpr splenocytes with IFN-alpha, and 4 were strongly downregulated. MRL/lpr lymphocytes were also found to be hyperresponsive to IFN-alpha. Thus, MRL/lpr lymphocytes overexpressed mRNA for the IFN-alpha receptor (IFNAR-1 and IFNAR-2) chains of the IFN-alpha/beta receptor and exhibited high endogenous levels of both Stat1 and phosphorylated Stat1 proteins. Lymphocytes from young MRL/lpr mice, with low Fas-dependent cytotoxic activity, were found to become highly cytotoxic against Fas+ targets after treatment with IFN-alpha. These data suggest that IFN-alpha plays an important role in the physiopathology of the systemic lupus erythematosus (SLE)-like syndrome that occurs in MRL/lpr mice.