SUMOylation-disrupting WAS mutation converts WASp from a transcriptional activator to a repressor of NF-κB response genes in T cells

Wiskott Aldrich syndrome protein (WASp)-deficient Th1 cells promote R-loop-driven transcriptional insufficiency and transcription-coupled nucleotide excision repair factor (TC-NER)-driven genome-instability in the pathogenesis of T cell acute lymphoblastic leukemia

BACKGROUND

T-ALL is an aggressive hematological tumor that develops as the result of a multi-step oncogenic process which causes expansion of hematopoietic progenitors that are primed for T cell development to undergo malignant transformation and growth. Even though first-line therapy has a significant response rate, 40% of adult patients and 20% of pediatric patients will relapse. Therefore, there is an unmet need for treatment for relapsed/refractory T-ALL to develop potential targeted therapies.

METHODS

Pediatric T-ALL patient derived T cells were grown under either nonskewingTh0 or Th1-skewing conditions to further process for ChIP-qPCR, RDIP-qPCR and other RT-PCR assays. Endogenous WASp was knocked out using CRISPR-Cas9 and was confirmed using flow cytometry and western blotting. LC-MS/MS was performed to find out proteomic dataset of WASp-interactors generated from Th1-skewed, human primary Th-cells. DNA-damage was assessed by immunofluorescence confocal-imaging and single-cell gel electrophoresis (comet assay). Overexpression of RNaseH1 was also done to restore normal Th1-transcription in WASp-deficient Th1-skewed cells.

RESULTS

We discovered that nuclear-WASp is required for suppressing R-loop production (RNA/DNA-hybrids) at Th1-network genes by ribonucleaseH2 (RNH2) and topoisomerase1. Nuclear-WASp is associated with the factors involved in preventing and dissolving R-loops in Th1 cells. In nuclear- WASp-reduced malignant Th1-cells, R-loops accumulate in vivo and are processed into DNA-breaks by transcription-coupled-nucleotide-excision repair (TC-NER). Several epigenetic modifications were also found to be involved at Th1 gene locus which are responsible for active/repressive marks of particular genes. By demonstrating WASp as a physiologic regulator of programmed versus unprogrammed R-loops, we suggest that the transcriptional role of WASp in vivo extends also to prevent transcription-linked DNA damage during malignancy and through modification of epigenetic dysregulations.

CONCLUSION

Our findings present a provocative possibility of resetting R-loops as a therapeutic intervention to correct both immune deficiency and malignancy in T-cell acute lymphoblastic leukemia patients and a novel role of WASp in the epigenetic regulation of T helper cell differentiation in T-ALL patients, anticipating WASp's requirement for the suppression of T-ALL progression.

Exploring the immunomodulatory potential of Brahmi (Bacopa monnieri) in the treatment of invasive ductal carcinoma

Bacopa monnieri (L) Wettst, commonly known as Brahmi, stands as a medicinal plant integral to India's traditional medical system, Ayurveda, where it is recognized as a "medhya rasayana"-a botanical entity believed to enhance intellect and mental clarity. Its significant role in numerous Ayurvedic formulations designed to address conditions such as anxiety, memory loss, impaired cognition, and diminished concentration underscores its prominence. Beyond its application in cognitive health, Brahmi has historically been employed in Ayurvedic practices for the treatment of inflammatory diseases, including arthritis. In contemporary biomedical research, Bacopa monnieri can attenuate the release of pro-inflammatory cytokines TNF-α and IL-6 in animal models. However, there remains a paucity of information regarding Bacopa's potential as an anticancer agent, warranting further investigation in this domain. Based on previous findings with Brahmi (Bacopa monnieri), the current study aims to find out the role of Brahmi plant preparation (BPP) in immunomodulatory actions on IDC. Employing a specific BPP concentration, we conducted a comprehensive study using MTT assay, ELISA, DNA methylation analysis, Western blotting, ChIP, and mRNA profiling to assess BPP's immunomodulatory properties. Our research finding showed the role of BPP in augmenting the action of T helper 1 (TH1) cells which secreted interferon-γ (IFN-γ) which in turn activated cytotoxic T-lymphocytes (CTL) to kill the cells of IDC (*p < 0.05). Moreover, we found out that treatment with BPP not only increased the activities of tumor-suppressor genes (p53 and BRCA1) but also decreased the activities of oncogenes (Notch1 and DNAPKcs) in IDC (*p < 0.05). BPP had an immense significance in controlling the epigenetic dysregulation in IDC through the downregulation of Histone demethylation & Histone deacetylation and upregulation of Histone methylation and Histone acetylation (*p < 0.05). Our Chromatin immunoprecipitation (ChIP)-qPCR data showed BPP treatment increased percentage enrichment of STAT1 & BRCA1 (*p < 0.05) and decreased percentage enrichment of STAT3, STAT5 & NF ΚB (*p < 0.05) on both TBX21 and BRCA1 gene loci in IDC. In addition, BPP treatment reduced the hypermethylation of the BRCA1-associated-DNA, which is believed to be a major factor in IDC (*p < 0.05). BPP not only escalates the secretion of type 1 specific cytokines but also escalates tumor suppression and harmonizes various epigenetic regulators and transcription factors associated with Signal Transducer and Activator of Transcription (STAT) to evoke tumor protective immunity in IDC.

Interplay between SUMO1-related SUMOylation and phosphorylation of p65 promotes hepatocellular carcinoma progression

The nuclear factor kappaB (NF-κB) subunit p65, plays an important role in the progression of hepatocellular carcinoma (HCC). Phosphorylation of p65 is considered as an important mechanism for the positive regulation of NF-κB activity. According to our previous data, p65 can be SUMOylated by small ubiquitin-related modifier 1 (SUMO1) protein, and SUMO1 promotes p65 nuclear import and HCC progression. However, the effect of SUMO1-related p65 SUMOylation on NF-κB transcriptional activity and the relationship between phosphorylation and SUMOylation of p65 remain obscure. Here, we found that phosphorylated p65 level was increased in cancer tissues of HCC patients, and similar phenomenon was found for SUMO1 expression but not for SUMO2/3. Further clinical data showed a positive correlation between SUMO1 and phosphorylated p65. We also verified that overexpression of SUMO1 upregulated phosphorylated p65 levels. Next, we verified SUMO1-related p65 SUMOylation with in vitro SUMOylation assay, constructed mutants of p65 SUMOylation and phosphorylation, and found that SUMO1-related p65 SUMOylation promoted p65 nuclear import and increased NF-κB activity. Both SUMO1-related p65 SUMOylation and p65 phosphorylation (especially at S276 site) increased the viability and invasion of hepatoma cells, and decreased the apoptosis of hepatoma cells. At last, we found that the phosphorylation of p65 promoted the level of SUMO1-related p65 SUMOylation, and SUMO1-related p65 SUMOylation upregulated phosphorylated p65 (at S276 site). Our study contributes to the exploration of the oncogenic mechanism of p65, which is the important protein in HCC.

Association of Wiskott-Aldrich syndrome protein (WASp) in epigenetic regulation of B cell differentiation in non-small-cell lung cancer (NSCLC)

Non-small-cell lung cancer (NSCLC) accounts for approximately 85% of all lung cancer which is the deadliest type of cancer for both men and women. Previous studies already showed that cell-intrinsic loss of WASp causes B cell tolerance and WASp deficiency in T helper (TH) cells is linked to negative effects on cytokine gene transcription necessary for TH1 differentiation. In the current study, we investigated the molecular mechanisms involved in WASp-mediated epigenetic regulation of B cell differentiation during NSCLC. Our ChIP-qPCR data suggest the less percentage enrichment of the B cell differentiating factors (Ikaros, Pax5, PU.1, BATF) and WASp across the WAS gene in the B cells of NSCLC patients in comparison with normal healthy donors and overexpression of WASp showed the reverse effects. WASp-depleted B cells while co-culturing with respective PBMCs isolated from normal healthy donors and NSCLC patients, we observed upregulation of TH2-, TH17-, and Treg-specific cytokines (IL4, ILI7A, IL10) & transcription factors (GATA3, RORC, FOXP3) and downregulation of TH1-specific cytokine (IFNγ) & transcription factor (TBX21). Our study showed that the overexpression of WASp resulted into upregulation of B cell differentiating factors, tumor suppressor protein (p53), histone methylation marker (H3K4me3) with concomitant downregulation of tumor-promoting factors (Notch 1, β-Catenin, DNAPKcs) and histone deacetylation marker (HDAC2) and increase in percentage cytotoxicity of NSCLC-specific cells (A549). Successful overexpression of WASp not only helps in epigenetic regulation of B cell differentiation but also supports tumor suppression in NSCLC. Thus, WASp can be targeted for therapeutic intervention of NSCLC.

Depletion of enhancer zeste homolog 2 (EZH2) directs transcription factors associated with T cell differentiation through epigenetic regulation of Yin Yang 1(YY1) in combating non-small cell lung cancer (NSCLC)

Non-Small Cell Lung Cancer (NSCLC) is the leading cause of death in all countries alike. In the current study, we have found out that Histone H3Lys4trimethylation is abnormal on YY1 in CD4⁺T Helper (T_H) cells of NSCLC patients which is evident by Histone H3Lys27 trimethylation mediated via EZH2. We investigated the status of Yin Yang 1 (YY1) and the involvement of certain transcription factors that lead to tumorigenesis after depleting endogenous EZH2 in vitro by CRISPR/Cas9 in the CD4⁺T_H1-or-T_H2-polarized cells isolated initially as CD4⁺T_H0 cells from the PBMC of the control subjects and patients suffering from NSCLC. After depletion of endogenous EZH2, RT-qPCR based mRNA expression analysis showed that there was an increase in the expression of T_H1 specific genes and a decrease in the expression of T_H2 specific genes in NSCLC patients CD4⁺T_H cells. We can conclude that this group of NSCLC patients may have the tendency at least in vitro to elucidate adaptive/protective immunity through the depletion of endogenous EZH2 along with the reduction in the expression of YY1. Moreover, depletion of EZH2 not only suppressed the CD4⁺CD25⁺FOXP3⁺Regulatory T cells (Treg) but also it aided the generation of CD8⁺Cytotoxic T Lymphocytes (CTL) which were involved in killing of the NSCLC cells. Thus the transcription factors involved in EZH2 mediated T cell differentiation linked to malignancies offers us an appealing avenue of targeted therapeutic intervention for NSCLC.

Understanding immunoactinopathies: A decade of research on WAS gene defects

Immunoactinopathies caused by mutations in actin-related proteins are a growing group of inborn errors of immunity (IEI). Immunoactinopathies are caused by a dysregulated actin cytoskeleton and affect hematopoietic cells especially because of their unique capacity to survey the body for invading pathogens and altered self, such as cancer cells. These cell motility and cell-to-cell interaction properties depend on the dynamic nature of the actin cytoskeleton. Wiskott-Aldrich syndrome (WAS) is the archetypical immunoactinopathy and the first described. WAS is caused by loss-of-function and gain-of-function mutations in the actin regulator WASp, uniquely expressed in hematopoietic cells. Mutations in WAS cause a profound disturbance of actin cytoskeleton regulation of hematopoietic cells. Studies during the last 10 years have shed light on the specific effects on different hematopoietic cells, revealing that they are not affected equally by mutations in the WAS gene. Moreover, the mechanistic understanding of how WASp controls nuclear and cytoplasmatic activities may help to find therapeutic alternatives according to the site of the mutation and clinical phenotypes. In this review, we summarize recent findings that have added to the complexity and increased our understanding of WAS-related diseases and immunoactinopathies.

Immunomodulatory Role of Diospyros peregrina Fruit Preparation in Breast Cancer by Utilizing Macrophage Mediated Antigen Presentation and T Helper Cell (Th) Differentiation

BACKGROUND

Diospyros peregrina is dioecious plant native to India and belonging to the family of Ebenaceae, is largely utilized in treatment of various ailments. Little has been known about the antitumor activity of Diospyros peregrina with only 1 previous study on Ehrlich Ascites Carcinoma in mice. Therefore, it prompted us to extensively explore the immunomodulatory effect in various cancer forms. The focal point of this study revolves around breast cancer, which is the second most common cancer in the world. In view of the increasing demands for noninvasive treatments, natural plant-based agents open up promising applications in cancer immunotherapy METHODS: CD4⁺ lymphocytes were isolated from the peripheral blood mononuclear cells (PBMCs) of breast cancer patients and normal donor blood samples using magnetic-activated cell sorting (MACS) and cultured separately. Utilizing the plastic surface adherence property, the macrophages were isolated from CD4 negative lymphocytes of both breast cancer patients and normal donors. For the presentation of tumor antigens invitro, macrophages were pulsed with breast tumor associated antigen (BTAA) in presence or absence of Diospyros peregrina fruit preparation (DFP). Differentially pulsed and irradiated macrophages were co-cultured with autologous and allogenic lymphocytes. Supernatants hence collected from CD4⁺ lymphocytes were utilized for cytokine profiling using ELISA and proliferation was assessed by MTT assay. Cytotoxic T lymphocytes (CTLs) generated from CD4 negative lymphocytes culture (2 × 10⁵) was incubated with MCF-7 (2 × 10⁴) to check cytotoxicity using LDH release assay. CD4⁺ lymphocytes were treated in presence or absence of DFP, were analyzed using immunoblotting and RT-qPCR, to check DFP mediated T helper (Th) cell differentiation through investigation of signatory cytokines and transcription factors.

RESULTS

It was found that DFP elevated the proliferation of CD4⁺ T lymphocytes (Th) in response to BTAA. DFP also helped in presenting BTAA pulsed macrophages directing in the cytotoxic T-lymphocyte mediated immune response. Results indicated that DFP preferentially highlighted Th1 commitment with type-1 specific cytokines IFN-g and IL-12 and was indifferent in Th2 manifestation. DFP was not only involved in the upregulation of Tbet mounted type-1 mediated immune response and activation of STAT1 but also it downregulated STAT6 and GATA3, the functional activators and regulators of type-2 immune response. Moreover, it was observed that DFP inhibited the tumor-promoting environment modulated through Tregs by downregulating Foxp3 and STAT5. Further, it was detected that DFP directs Th1 bias and results in attainment of better suppression of breast tumor CONCLUSION: The results collectively pointed out that DFP favored cell-mediated immune response from BTAA antigen presentation on macrophages and also helping in the robust proliferation of an entire spectrum of T helper lymphocytes which furthermore strengthen the underlying immune responses, hence, fencing the body, of the progression of breast cancer.

WASp modulates RPA function on single-stranded DNA in response to replication stress and DNA damage

Perturbation in the replication-stress response (RSR) and DNA-damage response (DDR) causes genomic instability. Genomic instability occurs in Wiskott-Aldrich syndrome (WAS), a primary immunodeficiency disorder, yet the mechanism remains largely uncharacterized. Replication protein A (RPA), a single-strand DNA (ssDNA) binding protein, has key roles in the RSR and DDR. Here we show that human WAS-protein (WASp) modulates RPA functions at perturbed replication forks (RFs). Following genotoxic insult, WASp accumulates at RFs, associates with RPA, and promotes RPA:ssDNA complexation. WASp deficiency in human lymphocytes destabilizes RPA:ssDNA-complexes, impairs accumulation of RPA, ATR, ETAA1, and TOPBP1 at genotoxin-perturbed RFs, decreases CHK1 activation, and provokes global RF dysfunction. las17 (yeast WAS-homolog)-deficient S. cerevisiae also show decreased ScRPA accumulation at perturbed RFs, impaired DNA recombination, and increased frequency of DNA double-strand break (DSB)-induced single-strand annealing (SSA). Consequently, WASp (or Las17)-deficient cells show increased frequency of DSBs upon genotoxic insult. Our study reveals an evolutionarily conserved, essential role of WASp in the DNA stress-resolution pathway, such that WASp deficiency provokes RPA dysfunction-coupled genomic instability.

Cancer develops in Wiskott-Aldrich syndrome (WAS). Here the authors identify a role for WAS-protein (WASp) in the DNA stress-resolution pathway by promoting the function of Replication Protein A at replication forks after DNA damage.

Reversion Mosaicism in Primary Immunodeficiency Diseases

Reversion mosaicism has been reported in an increasing number of genetic disorders including primary immunodeficiency diseases. Several mechanisms can mediate somatic reversion of inherited mutations. Back mutations restore wild-type sequences, whereas second-site mutations result in compensatory changes. In addition, intragenic recombination, chromosomal deletions, and copy-neutral loss of heterozygosity have been demonstrated in mosaic individuals. Revertant cells that have regained wild-type function may be associated with milder disease phenotypes in some immunodeficient patients with reversion mosaicism. Revertant cells can also be responsible for immune dysregulation. Studies identifying a large variety of genetic changes in the same individual further support a frequent occurrence of reversion mosaicism in primary immunodeficiency diseases. This phenomenon also provides unique opportunities to evaluate the biological effects of restored gene expression in different cell lineages. In this paper, we review the recent findings of reversion mosaicism in primary immunodeficiency diseases and discuss its clinical implications.

Deficiency of Wiskott-Aldrich syndrome protein has opposing effect on the pro-oncogenic pathway activation in nonmalignant versus malignant lymphocytes

Immunodeficiency is associated with cancer risk. Accordingly, hematolymphoid cancers develop in Wiskott-Aldrich syndrome (WAS), an X-linked primary immunodeficiency disorder (PID) resulting from the deficiency of WAS-protein (WASp) expressed predominantly in the hematolymphoid cell lineages. Despite the correlation between WASp deficiency and hematolymphoid cancers, the molecular mechanism underlying the oncogenic role of WASp is incompletely understood. Employing the WASp-sufficient and WASp-deficient cell-pair model of human T and B lymphocytes, we show that WASp deficiency differentially influences hyperactivation versus inhibition of both CDC42:ERK1/2 and NF-κB:AP-1 pro-oncogenic signaling pathways in nonmalignant versus malignant T and B lymphocytes. Furthermore, WASp deficiency induces a cell-type specific up/down-modulation of the DNA-binding activities of NF-κB, AP-1, and multiple other transcription factors with known roles in oncogenesis. We propose that WASp functions as a putative "tumor-suppressor" protein in normal T and B cells, and "oncoprotein" in a subset of established T and B cell malignancies that are not associated with the NPM-ALK fusion.

Interplay between Cytokine Circuitry and Transcriptional Regulation Shaping Helper T Cell Pathogenicity and Plasticity in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic disorder manifested as Crohn’s disease (CD) and ulcerative colitis (UC) characterized by intestinal inflammation and involves a dysregulated immune response against commensal microbiota through the activation of CD4 T helper cells. T helper cell differentiation to effector or regulatory phenotypes is controlled by cytokine networks and transcriptional regulators. Distinct polarized T helper cells are able to alter their phenotypes to adapt to diverse and fluctuating physiological environments. T helper cells exhibit intrinsic instability and flexibility to express cytokines of other lineages or transdifferentiate from one T helper cell type to another in response to various perturbations from physiological cytokine milieu as a means of promoting local immunity in response to injury or ensure tissue homeostasis. Furthermore, functional plasticity and diversity of T helper cells are associated with pathogenicity and are critical for immune homeostasis and prevention of autoimmunity. In this review, we provide deeper insights into the combinatorial extrinsic and intrinsic signals that control plasticity and transdifferentiation of T helper cells and also highlight the potential of exploiting the genetic reprogramming plasticity of T helper cells in the treatment of IBD.

Wiskott-Aldrich syndrome protein senses irradiation-induced DNA damage to coordinate the cell-protective Golgi dispersal response in human T and B lymphocytes

BACKGROUND

Wiskott-Aldrich syndrome (WAS) is an X-linked primary immune deficiency disorder resulting from Wiskott-Aldrich syndrome protein (WASp) deficiency. Lymphocytes from patients with WAS manifest increased DNA damage and lymphopenia from cell death, yet how WASp influences DNA damage-linked cell survival is unknown. A recently described mechanism promoting cell survival after ionizing radiation (IR)-induced DNA damage involves fragmentation and dispersal of the Golgi apparatus, known as the Golgi-dispersal response (GDR), which uses the Golgi phosphoprotein 3 (GOLPH3)-DNA-dependent protein kinase (DNA-PK)-myosin XVIIIA-F-actin signaling pathway.

OBJECTIVE

We sought to define WASp's role in the DNA damage-induced GDR and its disruption as a contributor to the development of radiosensitivity-linked immunodeficiency in patients with WAS.

METHODS

In human T_H and B-cell culture systems, DNA damage-induced GDR elicited by IR or radiomimetic chemotherapy was monitored in the presence or absence of WASp or GOLPH3 alone or both together.

RESULTS

WASp deficiency completely prevents the development of IR-induced GDR in human T_H and B cells, despite the high DNA damage load. Loss of WASp impedes nuclear translocation of GOLPH3 and its colocalization with the DNA-dependent protein kinase catalytic subunit (DNA-PKcs). Surprisingly, however, depletion of GOLPH3 alone or depolymerization of F-actin in WASp-sufficient T_H cells still allows development of robust GDR, suggesting that WASp, but not GOLPH3, is essential for GDR and cell survival after IR-induced DNA-damage in human lymphocytes.

CONCLUSION

The study identifies WASp as a novel effector of the nucleus-to-Golgi cell-survival pathway triggered by IR-induced DNA damage in cells of the hematolymphoid lineage and proposes an impaired GDR as a new cause for development of a "radiosensitive" form of immune dysregulation in patients with WAS.

Virus-Like Particles as an Instrument of Vaccine Production

The paper discusses the techniques which are currently implemented for vaccine production based on virus-like particles (VLPs). The factors which determine the characteristics of VLP monomers assembly are provided in detail. Analysis of the literature demonstrates that the development of the techniques of VLP production and immobilization of target antigens on their surface have led to the development of universal platforms which make it possible for virtually any known antigen to be exposed on the particle surface in a highly concentrated form. As a result, the focus of attention has shifted from the approaches to VLP production to the development of a precise interface between the organism's immune system and the peptides inducing a strong immune response to pathogens or the organism's own pathological cells. Immunome-specified methods for vaccine design and the prospects of immunoprophylaxis are discussed. Certain examples of vaccines against viral diseases and cancers are considered.

miR-221 alleviates the inflammatory response and cell apoptosis of neuronal cell through targeting TNFAIP2 in spinal cord ischemia-reperfusion

This study aimed to examine the role of miR-221 in inflammatory response and apoptosis of neuronal cells after spinal cord ischemia/reperfusion (I/R) injury. Blood samples were obtained from 20 I/R patients and that of 20 healthy individuals were used as a control. AGE1.HN and SY-SH-5Y neuronal cell lines subjected to oxygen-glucose deprivation (OGD) stress were used in cell experiments. Real-time PCR and western blot were used to evaluate the expression of miR-221, tumor necrosis factor-α, and TNFAIP2. TUNEL assay analyzed cell apoptosis. I/R patients had lower serum levels of miR-221 than healthy controls. In OGD-AGE1.HN and SY-SH-5Y cells, miR-221 was significantly downregulated and TNFAIP2 mRNA and protein were upregulated; meanwhile, both proinflammatory cytokine tumor necrosis factor-α and anti-inflammation cytokine interleukin-6 were elevated and the percentage of apoptotic cells was increased. This inflammatory response and cell apoptosis induced by OGD stress were attenuated by miR-221 overexpression and enhanced by miR-221 knockdown. TNFAIP2 is a target gene for miR-221 and could be regulated negatively by the miR-221 mimic or the miR-221 inhibitor with or without OGD stress. Accordingly, TNFAIP2 overexpression reversed the inflammatory response and cell apoptosis induced by miR-221 under OGD stress. Downregulation of miR-221 occurs in spinal cord I/R injury and in cell lines subjected to oxygen-glucose deprivation. miR-221 regulates the inflammatory response and apoptosis of neuronal cells through its impact on TNFAIP2.

Transcription factor Zbtb38 downregulates the expression of anti-inflammatory IL1r2 in mouse model of rheumatoid arthritis

DNA methylation is a decisive regulator of gene expression. Differentially methylated promoters were described in rheumatoid arthritis (RA), but we do not know how these epimutations can trigger a proinflammatory cytokine milieu. B cell-focused DNA methylome studies identified a group of genes that had undergone disease-associated changes in a murine model of RA. An arthritis-specific epimutation (hypomethylation) was detected in the promoter region of the Zbtb38 gene, which encodes a transcriptional repressor. Gene expression studies revealed that hypomethylation of the Zbtb38 promoter was accompanied by disease-specific repressor expression, and two anti-inflammatory factors interleukin 1 receptor 2 gene (IL1r2) and interleukin-1 receptor antagonist (IL1rn) were among the downregulated genes. We hypothesized that Zbtb38 repressor could induce downregulated expression of these anti-inflammatory genes and that this could significantly contribute to arthritis pathogenesis. Our studies demonstrate that Zbtb38 forms a molecular bridge between an arthritis-associated epimutation (DNA hypomethylation in Zbtb38 promoter) and transcriptional silencing of the IL1r2 gene in B cells. In this way, disease-associated DNA hypomethylation can support autoimmune arthritis by interfering with an anti-inflammatory pathway.

DeSUMOylation of MKK7 kinase by the SUMO2/3 protease SENP3 potentiates lipopolysaccharide-induced inflammatory signaling in macrophages

Protein SUMOylation has been reported to play a role in innate immune response, but the enzymes, substrates, and consequences of the specific inflammatory signaling events are largely unknown. Reactive oxygen species (ROS) are abundantly produced during macrophage activation and required for Toll-like receptor 4 (TLR4)-mediated inflammatory signaling. Previously, we demonstrated that SENP3 is a redox-sensitive SUMO2/3 protease. To explore any links between reversible SUMOylation and ROS-related inflammatory signaling in macrophage activation, we generated mice with Senp3 conditional knock-out in myeloid cells. In bacterial lipopolysaccharide (LPS)-induced in vitro and in vivo inflammation models, we found that SENP3 deficiency markedly compromises the activation of TLR4 inflammatory signaling and the production of proinflammatory cytokines in macrophages exposed to LPS. Moreover, Senp3 conditional knock-out mice were significantly less susceptible to septic shock. Of note, SENP3 deficiency was associated with impairment in JNK phosphorylation. We found that MKK7, which selectively phosphorylates JNK, is a SENP3 substrate and that SENP3-mediated deSUMOylation of MKK7 may favor its binding to JNK. Importantly, ROS-dependent SENP3 accumulation and MKK7 deSUMOylation rapidly occurred after LPS stimulation. In conclusion, our findings indicate that SENP3 potentiates LPS-induced TLR4 signaling via deSUMOylation of MKK7 leading to enhancement in JNK phosphorylation and the downstream events. Therefore this work provides novel mechanistic insights into redox regulation of innate immune responses.

R-loops cause genomic instability in T helper lymphocytes from patients with Wiskott-Aldrich syndrome

BACKGROUND

Wiskott-Aldrich syndrome (WAS), X-linked thrombocytopenia (XLT), and X-linked neutropenia, which are caused by WAS mutations affecting Wiskott-Aldrich syndrome protein (WASp) expression or activity, manifest in immunodeficiency, autoimmunity, genomic instability, and lymphoid and other cancers. WASp supports filamentous actin formation in the cytoplasm and gene transcription in the nucleus. Although the genetic basis for XLT/WAS has been clarified, the relationships between mutant forms of WASp and the diverse features of these disorders remain ill-defined.

OBJECTIVE

We sought to define how dysfunctional gene transcription is causally linked to the degree of T_H cell deficiency and genomic instability in the XLT/WAS clinical spectrum.

METHODS

In human T_H1- or T_H2-skewing cell culture systems, cotranscriptional R-loops (RNA/DNA duplex and displaced single-stranded DNA) and DNA double-strand breaks (DSBs) were monitored in multiple samples from patients with XLT and WAS and in normal T cells depleted of WASp.

RESULTS

WASp deficiency provokes increased R-loops and R-loop-mediated DSBs in T_H1 cells relative to T_H2 cells. Mechanistically, chromatin occupancy of serine 2-unphosphorylated RNA polymerase II is increased, and that of topoisomerase 1, an R-loop preventing factor, is decreased at R-loop-enriched regions of IFNG and TBX21 (T_H1 genes) in T_H1 cells. These aberrations accompany increased unspliced (intron-retained) and decreased spliced mRNA of IFNG and TBX21 but not IL13 (T_H2 gene). Significantly, increased cellular load of R-loops and DSBs, which are normalized on RNaseH1-mediated suppression of ectopic R-loops, inversely correlates with disease severity scores.

CONCLUSION

Transcriptional R-loop imbalance is a novel molecular defect causative in T_H1 immunodeficiency and genomic instability in patients with WAS. The study proposes that cellular R-loop load could be used as a potential biomarker for monitoring symptom severity and prognostic outcome in the XLT-WAS clinical spectrum and could be targeted therapeutically.

Nuclear Wiskott-Aldrich syndrome protein co-regulates T cell factor 1-mediated transcription in T cells

BACKGROUND

The Wiskott-Aldrich syndrome protein (WASp) family of actin-nucleating factors are present in the cytoplasm and in the nucleus. The role of nuclear WASp for T cell development remains incompletely defined.

METHODS

We performed WASp chromatin immunoprecipitation and deep sequencing (ChIP-seq) in thymocytes and spleen CD4⁺ T cells.

RESULTS

WASp was enriched at genic and intergenic regions and associated with the transcription start sites of protein-coding genes. Thymocytes and spleen CD4⁺ T cells showed 15 common WASp-interacting genes, including the gene encoding T cell factor (TCF)12. WASp KO thymocytes had reduced nuclear TCF12 whereas thymocytes expressing constitutively active WASp^L272P and WASp^I296T had increased nuclear TCF12, suggesting that regulated WASp activity controlled nuclear TCF12. We identify a putative DNA element enriched in WASp ChIP-seq samples identical to a TCF1-binding site and we show that WASp directly interacted with TCF1 in the nucleus.

CONCLUSIONS

These data place nuclear WASp in proximity with TCF1 and TCF12, essential factors for T cell development.

Cellular functions of WASP family proteins at a glance

Proteins of the Wiskott-Aldrich syndrome protein (WASP) family function as nucleation-promoting factors for the ubiquitously expressed Arp2/3 complex, which drives the generation of branched actin filaments. Arp2/3-generated actin regulates diverse cellular processes, including the formation of lamellipodia and filopodia, endocytosis and/or phagocytosis at the plasma membrane, and the generation of cargo-laden vesicles from organelles including the Golgi, endoplasmic reticulum (ER) and the endo-lysosomal network. Recent studies have also identified roles for WASP family members in promoting actin dynamics at the centrosome, influencing nuclear shape and membrane remodeling events leading to the generation of autophagosomes. Interestingly, several WASP family members have also been observed in the nucleus where they directly influence gene expression by serving as molecular platforms for the assembly of epigenetic and transcriptional machinery. In this Cell Science at a Glance article and accompanying poster, we provide an update on the subcellular roles of WHAMM, JMY and WASH (also known as WASHC1), as well as their mechanisms of regulation and emerging functions within the cell.

Chromatin Association of Gcn4 Is Limited by Post-translational Modifications Triggered by its DNA-Binding in Saccharomyces cerevisiae

The Saccharomyces cerevisiae transcription factor Gcn4 is expressed during amino acid starvation, and its abundance is controlled by ubiquitin-mediated proteolysis. Cdk8, a kinase component of the RNA polymerase II Mediator complex, phosphorylates Gcn4, which triggers its ubiquitination/proteolysis, and is thought to link Gcn4 degradation with transcription of target genes. In addition to phosphorylation and ubiquitination, we previously showed that Gcn4 becomes sumoylated in a DNA-binding dependent manner, while a nonsumoylatable form of Gcn4 showed increased chromatin occupancy, but only if Cdk8 was present. To further investigate how the association of Gcn4 with chromatin is regulated, here we examine determinants for Gcn4 sumoylation, and how its post-translational modifications are coordinated. Remarkably, artificially targeting Gcn4 that lacks its DNA binding domain to a heterologous DNA site restores sumoylation at its natural modification sites, indicating that DNA binding is sufficient for the modification to occur in vivo Indeed, we find that neither transcription of target genes nor phosphorylation are required for Gcn4 sumoylation, but blocking its sumoylation alters its phosphorylation and ubiquitination patterns, placing Gcn4 sumoylation upstream of these Cdk8-mediated modifications. Strongly supporting a role for sumoylation in limiting its association with chromatin, a hyper-sumoylated form of Gcn4 shows dramatically reduced DNA occupancy and expression of target genes. Importantly, we find that Cdk8 is at least partly responsible for clearing hyper-sumoylated Gcn4 from DNA, further implicating sumoylation as a stimulus for Cdk8-mediated phosphorylation and degradation. These results support a novel function for SUMO in marking the DNA-bound form of a transcription factor, which triggers downstream processes that limit its association with chromatin, thus preventing uncontrolled expression of target genes.

The early activation of memory B cells from Wiskott-Aldrich syndrome patients is suppressed by CD19 downregulation

Wiskott-Aldrich syndrome (WAS) pediatric patients exhibit a deficiency in humoral immune memory. However, the mechanism by which Wiskott-Aldrich syndrome protein (WASP) regulates the differentiation and activation of memory B cells remains elusive. Here we examine the early activation events of memory B cells from the peripheral blood mononuclear cells of WAS patients and age-matched healthy controls (HCs) using total internal reflection fluorescence microscopy. In response to stimulation through the B-cell receptor (BCR), memory B cells from HCs showed significantly higher magnitudes of BCR clustering and cell spreading than naive B cells from the same individuals. This was associated with increases in CD19 recruitment to the BCR and the activation of its downstream signaling molecule Btk and decreases in FcγRIIB recruitment and the activation of its downstream molecule Src homology 2-containing inositol 5' phosphatase (SHIP). However, these enhanced signaling activities mediated by CD19 and Btk are blocked in memory B cells from WAS patients, whereas the activation of FcγRIIB and SHIP was increased. Although the expression levels of CD19, Btk, and FcγRIIB did not change between CD27(-) and CD27(+) B cells of HCs, the protein and mRNA levels of CD19 but not Btk and FcγRIIB were significantly reduced in both CD27(-) and CD27(+) B cells of WAS patients, compared with those of HCs. Overall, our study suggests that WASP is required for memory B-cell activation, promoting the activation by positive regulating CD19 transcription and CD19 recruitment to the BCR.

Abnormalities of follicular helper T-cell number and function in Wiskott-Aldrich syndrome

Wiskott-Aldrich syndrome protein (WASp) is a hematopoietic-specific regulator of actin nucleation. Wiskott-Aldrich syndrome (WAS) patients show immunodeficiencies, most of which have been attributed to defective T-cell functions. T follicular helper (Tfh) cells are the major CD4(+) T-cell subset with specialized B-cell helper capabilities. Aberrant Tfh cells activities are involved in immunopathologies such as autoimmunity, immunodeficiencies, and lymphomas. We found that in WAS patients, the number of circulating Tfh cells was significantly reduced due to reduced proliferation and increased apoptosis, and Tfh cells were Th2 and Th17 polarized. The expression of inducible costimulator (ICOS) in circulating Tfh cells was higher in WAS patients than in controls. BCL6 expression was decreased in total CD4(+) T and Tfh cells of WAS patients. Mirroring the results in patients, the frequency of Tfh cells in WAS knockout (KO) mice was decreased, as was the frequency of BCL6(+) Tfh cells, but the frequency of ICOS(+) Tfh cells was increased. Using WAS chimera mice, we found that the number of ICOS(+) Tfh cells was decreased in WAS chimera mice, indicating that the increase in ICOS(+) Tfh cells in WAS KO mice was cell extrinsic. The data from in vivo CD4(+) naive T-cell adoptive transfer mice as well as in vitro coculture of naive B and Tfh cells showed that the defective function of WASp-deficient Tfh cells was T-cell intrinsic. Consistent findings in both WAS patients and WAS KO mice suggested an essential role for WASp in the development and memory response of Tfh cells and that WASp deficiency causes a deficient differentiation defect in Tfh cells by downregulating the transcription level of BCL6.