BTB-ZF transcription factors, a growing family of regulators of early and late B-cell development

The genetic architecture of complete blood counts in lactating Holstein dairy cows

Complete blood counts (CBCs) measure the abundance of individual immune cells, red blood cells, and related measures such as platelets in circulating blood. These measures can indicate the health status of an animal; thus, baseline circulating levels in a healthy animal may be related to the productive life, resilience, and production efficiency of cattle. The objective of this study is to determine the heritability of CBC traits and identify genomic regions that are associated with CBC measurements in lactating Holstein dairy cattle. The heritability of CBCs was estimated using a Bayes C0 model. The study population consisted of 388 cows with genotypes at roughly 75,000 markers and 16 different CBC phenotypes taken at one to three time points (n = 33, 131, and 224 for 1, 2, and 3 time points, respectively). Heritabilities ranged from 0.00 ± 0.00 (red cell distribution width) to 0.68 ± 0.06 (lymphocytes). A total of 96 different 1-Mb windows were identified that explained more than 1% of the genetic variance for at least one CBC trait, with 10 windows explaining more than 1% of the genetic variance for two or more traits. Multiple genes in the identified regions have functions related to immune response, cell differentiation, anemia, and disease. Positional candidate genes include RAD52 motif-containing protein 1 (RDM1), which is correlated with the degree of immune infiltration of immune cells, and C-X-C motif chemokine ligand 12 (CXCL12), which is critically involved in neutrophil bone marrow storage and release regulation and enhances neutrophil migration. Since animal health directly impacts feed intake, understanding the genetics of CBCs may be useful in identifying more disease-resilient and feed-efficient dairy cattle. Identification of genes responsible for variation in CBCs will also help identify the variability in how dairy cattle defend against illness and injury.

Dimerization choice and alternative functions of ZBTB transcription factors

Zinc Finger DNA-binding domain-containing proteins are the most populous family among eukaryotic transcription factors. Among these, members of the BTB domain-containing ZBTB sub-family are mostly known for their transcriptional repressive functions. In this Viewpoint article, we explore molecular mechanisms that potentially diversify the function of ZBTB proteins based on their homo and heterodimerization, alternative splicing and post-translational modifications. We describe how the BTB domain is as much a scaffold for the assembly of co-repressors, as a domain that regulates protein stability. We highlight another mechanism that regulates ZBTB protein stability: phosphorylation in the zinc finger domain. We explore the non-transcriptional, structural roles of ZBTB proteins and highlight novel findings that describe the ability of ZBTB proteins to associate with poly adenosine ribose in the nucleus during the DNA damage response. Herein, we discuss the contribution of BTB domain scaffolds to the formation of transcriptional repressive complexes, to chromosome compartmentalization and their non-transcriptional, purely structural functions in the nucleus.

Late fetal hematopoietic failure results from ZBTB11 deficiency despite abundant HSC specification

Hematopoiesis produces diverse blood cell lineages to meet the basal needs and sudden demands of injury or infection. A rapid response to such challenges requires the expansion of specific lineages and a prompt return to balanced steady-state levels, necessitating tightly coordinated regulation. Previously we identified a requirement for the zinc finger and broad complex, tramtrak, bric-a-brac domain-containing 11 (ZBTB11) transcription factor in definitive hematopoiesis using a forward genetic screen for zebrafish myeloid mutants. To understand its relevance to mammalian systems, we extended these studies to mice. When Zbtb11 was deleted in the hematopoietic compartment, embryos died at embryonic day (E) 18.5 with hematopoietic failure. Zbtb11 hematopoietic knockout (Zbtb11hKO) hematopoietic stem cells (HSCs) were overabundantly specified from E14.5 to E17.5 compared with those in controls. Overspecification was accompanied by loss of stemness, inability to differentiate into committed progenitors and mature lineages in the fetal liver, failure to seed fetal bone marrow, and total hematopoietic failure. The Zbtb11hKO HSCs did not proliferate in vitro and were constrained in cell cycle progression, demonstrating the cell-intrinsic role of Zbtb11 in proliferation and cell cycle regulation in mammalian HSCs. Single-cell RNA sequencing analysis identified that Zbtb11-deficient HSCs were underrepresented in an erythroid-primed subpopulation and showed downregulation of oxidative phosphorylation pathways and dysregulation of genes associated with the hematopoietic niche. We identified a cell-intrinsic requirement for Zbtb11-mediated gene regulatory networks in sustaining a pool of maturation-capable HSCs and progenitor cells.

Sibling rivalry among the ZBTB transcription factor family: homodimers versus heterodimers

BTB domains potentially can form homo- or heterodimers. The study examines the dimerization choice of several BTB domains and finds only one heterodimer, while all tested pairs can homodimerize.

The BTB domain is an oligomerization domain found in over 300 proteins encoded in the human genome. In the family of BTB domain and zinc finger–containing (ZBTB) transcription factors, 49 members share the same protein architecture. The N-terminal BTB domain is structurally conserved among the family members and serves as the dimerization site, whereas the C-terminal zinc finger motifs mediate DNA binding. The available BTB domain structures from this family reveal a natural inclination for homodimerization. In this study, we investigated the potential for heterodimer formation in the cellular environment. We selected five BTB homodimers and four heterodimer structures. We performed cell-based binding assays with fluorescent protein–BTB domain fusions to assess dimer formation. We tested the binding of several BTB pairs, and we were able to confirm the heterodimeric physical interaction between the BTB domains of PATZ1 and PATZ2, previously reported only in an interactome mapping experiment. We also found this pair to be co-expressed in several immune system cell types. Finally, we used the available structures of BTB domain dimers and newly constructed models in extended molecular dynamics simulations (500 ns) to understand the energetic determinants of homo- and heterodimer formation. We conclude that heterodimer formation, although frequently described as less preferred than homodimers, is a possible mechanism to increase the combinatorial specificity of this transcription factor family.

Contribution of ZBTB20 Polymorphisms to Esophageal Cancer Risk Among the Chinese Han Population

Background

ZBTB20 was overexpressed in esophageal cancer (EC). The study aimed to identify genotypes of ZBTB20 polymorphisms and their correlation with EC occurrence in a Chinese Han population.

Methods

Four single nucleotide polymorphisms (SNPs) in ZBTB20 were randomly selected for genotyping through Agena MassARRAY system among 525 EC patients and 522 healthy controls. Multiple genetic models were applied to assess the association of ZBTB20 polymorphisms with EC susceptibility by calculating odds ratios (ORs) with 95% confidence intervals (CIs).

Results

Rs10934270 was associated with lower EC susceptibility (OR = 0.64, p = 0.004) with statistical power >90% in overall analysis. Specifically, the correlation of rs10934270 with EC susceptibility was found in subgroups including patients with esophageal squamous cell carcinoma (ESCC), males, subjects aged ≤65 years, subjects with BMI ≤ 24 kg/m², and smokers. Rs9841504 might be a risk-increasing factor for ESCC. Moreover, rs9288999 in subjects aged ≤65 years and rs73230612 in females were related to lower EC risk.

Conclusion

Our research is the first to report that ZBTB20 rs10934270 is associated with reduced EC susceptibility in the Chinese Han population. These data provide a scientific basis for understanding the influence of the ZBTB20 gene on EC occurrence.

ZBTB20 regulates cardiac allograft rejection through NFкB-mediated inflammation in mouse heart transplantation

Allograft rejection is a major obstacle for the long-term survival of heart transplantation (Htx) patients. The cardiac allograft rejection requires the activation of macrophages and effector T cells. In this study, we explored the role of zinc-finger and BTB domain containing protein 20 (ZBTB20) in the regulation of heart allograft rejection. Flow cytometry analysis of the spleen cells from mice undergoing an acute cardiac rejection revealed that the ZBTB20 protein expression was upregulated in both T and B cells(n = 4，P < 0.01). In addition, ZBTB20 gene knockdown significantly prolonged the survival of heart allografts in mice(n = 4，P < 0.01). Lack of ZBTB20 increased the expression of Foxp3 and limited the response of T helper 1 (Th1) cells(n = 4，P < 0.01). The ZBTB20-related regulation occurred through the activation of the NFкB pathway. In conclusion, our data suggest that ZBTB20 is involved in the regulation of T cells involved in acute heart allograft rejection. Hence, downregulation of ZBTB20 expression may inhibit T cells to prolong heart transplant survival.

Zbtb20 identifies and controls a thymus-derived population of regulatory T cells that play a role in intestinal homeostasis

The expression of BTB-ZF transcription factors such as ThPOK in CD4⁺ T cells, Bcl6 in T follicular helper cells, and PLZF in natural killer T cells defines the fundamental nature and characteristics of these cells. Screening for lineage-defining BTB-ZF genes led to the discovery of a subset of T cells that expressed Zbtb20. About half of Zbtb20⁺ T cells expressed FoxP3, the lineage-defining transcription factor for regulatory T cells (T_regs). Zbtb20⁺ T_regs were phenotypically and genetically distinct from the larger conventional T_reg population. Zbtb20⁺ T_regs constitutively expressed mRNA for interleukin-10 and produced high levels of the cytokine upon primary activation. Zbtb20⁺ T_regs were enriched in the intestine and specifically expanded when inflammation was induced by the use of dextran sodium sulfate. Conditional deletion of Zbtb20 in T cells resulted in a loss of intestinal epithelial barrier integrity. Consequently, knockout (KO) mice were acutely sensitive to colitis and often died because of the disease. Adoptive transfer of Zbtb20⁺ T_regs protected the Zbtb20 conditional KO mice from severe colitis and death, whereas non-Zbtb20 T_regs did not. Zbtb20 was detected in CD24^hi double-positive and CD62L^lo CD4 single-positive thymocytes, suggesting that expression of the transcription factor and the phenotype of these cells were induced during thymic development. However, Zbtb20 expression was not induced in "conventional" T_regs by activation in vitro or in vivo. Thus, Zbtb20 expression identified and controlled the function of a distinct subset of T_regs that are involved in intestinal homeostasis.

Quality control of protein complex assembly by the ubiquitin-proteasome system

The majority of human proteins operate as multimeric complexes with defined compositions and distinct architectures. How the assembly of these complexes is surveyed and how defective complexes are recognized is just beginning to emerge. In eukaryotes, over 600 E3 ubiquitin ligases form part of the ubiquitin-proteasome system (UPS) which detects structural characteristics in its target proteins and selectively induces their degradation. The UPS has recently been shown to oversee key quality control steps during the assembly of protein complexes. We review recent findings on how E3 ubiquitin ligases regulate protein complex assembly and highlight unanswered questions relating to their mechanism of action.

ZBTB11 dysfunction: spectrum of brain abnormalities, biochemical signature and cellular consequences

Bi-allelic pathogenic variants in ZBTB11 have been associated with intellectual developmental disorder, autosomal recessive 69 (MRT69; OMIM 618383). We report five patients from three families with novel, bi-allelic variants in ZBTB11. We have expanded the clinical phenotype of MRT69, documenting varied severity of atrophy affecting different brain regions and described combined malonic and methylmalonic aciduria as a biochemical manifestation. As ZBTB11 encodes for a transcriptional regulator, we performeded chromatin immunoprecipitation-sequencing targeting ZBTB11 in fibroblasts from patients and controls. Chromatin immunoprecipitation-sequencing revealed binding of wild-type ZBTB11 to promoters in 238 genes, among which genes encoding proteins involved in mitochondrial functions and RNA processing are over-represented. Mutated ZBTB11 showed reduced binding to 61 of the targeted genes, indicating that the variants act as loss of function. Most of these genes are related to mitochondrial functions. Transcriptome analysis of the patient fibroblasts revealed dysregulation of mitochondrial functions. In addition, we uncovered that reduced binding of the mutated ZBTB11 to ACSF3 leads to decreased ACSF3 transcript level, explaining combined malonic and methylmalonic aciduria. Collectively, these results expand the clinical spectrum of ZBTB11-related neurological disease and give insight into the pathophysiology in which the dysfunctional ZBTB11 affect mitochondrial functions and RNA processing contributing to the neurological and biochemical phenotypes.

DUBR suppresses migration and invasion of human lung adenocarcinoma cells via ZBTB11-mediated inhibition of oxidative phosphorylation

Long noncoding RNAs (lncRNAs) are involved in a variety of cancers, but the role of LncRNA DUBR in lung adenocarcinoma (LUAD), the most prevalent form of lung cancer, remains unclear. In this study we investigated the expression of DUBR in LUAD to ascertain its association with the clinical pathology and prognosis of LUAD. Analysis of mRNA expression in The Cancer Genome Atlas (TCGA) LUAD database and in-house LUAD cohort (n = 94) showed that DUBR was significantly downregulated in LUAD, and was associated with poor prognosis. In LUAD cell lines (H1975, A549), overexpression of DUBR significantly suppressed the migration and invasion of the LUAD cells. We demonstrated that c-Myc could bind to the promoter of DUBR, and transcriptionally suppressed its expression. Knockdown of c-Myc almost completely blocked the invasion and migration of LUAD cells, whereas knockdown of DUBR partially rescued c-Myc-knockdown suppressed cell migration and invasion. Furthermore, DUBR overexpression significantly increased the expression of a downstream protein of DUBR, zinc finger, and BTB domain containing 11 (ZBTB11), in H1975 and A549 cells; knockdown of ZBTB11 partially rescued the DUBR-overexpression suppressed cell migration and invasion; knockdown of c-Myc significantly upregulated the expression of ZBTB11 in LUAD cells. Finally, we revealed that DUBR/ZBTB11 axis suppressed oxidative phosphorylation in LUAD cells. In short, we demonstrate that c-Myc/DUBR/ZBTB11 axis suppresses migration and invasion of LUAD by attenuating cell oxidative phosphorylation, which provides new insights into the regulatory mechanism of DUBR.

Single nucleotide variations in ZBTB46 are associated with post-thrombolytic parenchymal haematoma

Haemorrhagic transformation is a complication of recombinant tissue-plasminogen activator treatment. The most severe form, parenchymal haematoma, can result in neurological deterioration, disability, and death. Our objective was to identify single nucleotide variations associated with a risk of parenchymal haematoma following thrombolytic therapy in patients with acute ischaemic stroke. A fixed-effect genome-wide meta-analysis was performed combining two-stage genome-wide association studies (n = 1904). The discovery stage (three cohorts) comprised 1324 ischaemic stroke individuals, 5.4% of whom had a parenchymal haematoma. Genetic variants yielding a P-value < 0.05 1 × 10-5 were analysed in the validation stage (six cohorts), formed by 580 ischaemic stroke patients with 12.1% haemorrhagic events. All participants received recombinant tissue-plasminogen activator; cases were parenchymal haematoma type 1 or 2 as defined by the European Cooperative Acute Stroke Study (ECASS) criteria. Genome-wide significant findings (P < 5 × 10-8) were characterized by in silico functional annotation, gene expression, and DNA regulatory elements. We analysed 7 989 272 single nucleotide polymorphisms and identified a genome-wide association locus on chromosome 20 in the discovery cohort; functional annotation indicated that the ZBTB46 gene was driving the association for chromosome 20. The top single nucleotide polymorphism was rs76484331 in the ZBTB46 gene [P = 2.49 × 10-8; odds ratio (OR): 11.21; 95% confidence interval (CI): 4.82-26.55]. In the replication cohort (n = 580), the rs76484331 polymorphism was associated with parenchymal haematoma (P = 0.01), and the overall association after meta-analysis increased (P = 1.61 × 10-8; OR: 5.84; 95% CI: 3.16-10.76). ZBTB46 codes the zinc finger and BTB domain-containing protein 46 that acts as a transcription factor. In silico studies indicated that ZBTB46 is expressed in brain tissue by neurons and endothelial cells. Moreover, rs76484331 interacts with the promoter sites located at 20q13. In conclusion, we identified single nucleotide variants in the ZBTB46 gene associated with a higher risk of parenchymal haematoma following recombinant tissue-plasminogen activator treatment.

The BTB-domain transcription factor ZBTB2 recruits chromatin remodelers and a histone chaperone during the exit from pluripotency

Transcription factors (TFs) harboring broad-complex, tramtrack, and bric-a-brac (BTB) domains play important roles in development and disease. These BTB domains are thought to recruit transcriptional modulators to target DNA regions. However, a systematic molecular understanding of the mechanism of action of this TF family is lacking. Here, we identify the zinc finger BTB-TF Zbtb2 from a genetic screen for regulators of exit from pluripotency and demonstrate that its absence perturbs embryonic stem cell differentiation and the gene expression dynamics underlying peri-implantation development. We show that ZBTB2 binds the chromatin remodeler Ep400 to mediate downstream transcription. Independently, the BTB domain directly interacts with nucleosome remodeling and deacetylase and histone chaperone histone regulator A. Nucleosome remodeling and deacetylase recruitment is a common feature of BTB TFs, and based on phylogenetic analysis, we propose that this is a conserved evolutionary property. Binding to UBN2, in contrast, is specific to ZBTB2 and requires a C-terminal extension of the BTB domain. Taken together, this study identifies a BTB-domain TF that recruits chromatin modifiers and a histone chaperone during a developmental cell state transition and defines unique and shared molecular functions of the BTB-domain TF family.

ZBTB38 is dispensable for antibody responses

Members of the broad complex, tram track, bric-a-brac and zinc finger (BTB-ZF) family of transcription factors, such as BCL-6, ZBTB20, and ZBTB32, regulate antigen-specific B cell differentiation, plasma cell longevity, and the duration of antibody production. We found that ZBTB38, a different member of the BTB-ZF family that binds methylated DNA at CpG motifs, is highly expressed by germinal center B cells and plasma cells. To define the functional role of ZBTB38 in B cell responses, we generated mice conditionally deficient in this transcription factor. Germinal center B cells lacking ZBTB38 dysregulated very few genes relative to wild-type and heterozygous littermate controls. Accordingly, mice with hematopoietic-specific deletion of Zbtb38 showed normal germinal center B cell numbers and antibody responses following immunization with hapten-protein conjugates. Memory B cells from these animals functioned normally in secondary recall responses. Despite expression of ZBTB38 in hematopoietic stem cells, progenitors and mature myeloid and lymphoid lineages were also present in normal numbers in mutant mice. These data demonstrate that ZBTB38 is dispensable for hematopoiesis and antibody responses. These conditional knockout mice may instead be useful in defining the functional importance of ZBTB38 in other cell types and contexts.

Zbtb20 deficiency causes cardiac contractile dysfunction in mice

The zinc-finger protein ZBTB20 regulates development and metabolism in multiple systems, and is essential for postnatal survival in mice. However, its potential role in the cardiovascular system remains undefined. Here, we demonstrate that ZBTB20 is critically involved in the regulation of cardiac contractility and blood pressure in mice. At the age of 16 days, the relatively healthy Zbtb20-null mice exhibited hypotension without obvious change of heart rate or other evidence for heart failure. Moreover, Zbtb20 deletion led to a marked reduction in heart size, left ventricular wall thickness, and cell size of cardiomyocytes, which was largely proportional to the decreased body growth. Notably, echocardiographic and hemodynamic analyses showed that cardiac contractility was greatly impaired in the absence of ZBTB20. Mechanistically, ZBTB20 deficiency decreased cardiac ATP contents, and compromised the enzyme activity of mitochondrial complex I in heart as well as L-type calcium current density in cardiomyocytes. Furthermore, the developmental activation of some mitochondrial function-related genes was significantly attenuated in Zbtb20-null myocardium, which included Hspb8, Ckmt2, Cox7a1, Tfrc, and Ogdhl. Put together, these results suggest that ZBTB20 plays a crucial role in the regulation of heart development, energy metabolism, and contractility.

Structural analysis of the PATZ1 BTB domain homodimer

PATZ1 is a ubiquitously expressed transcriptional repressor belonging to the ZBTB family that is functionally expressed in T lymphocytes. PATZ1 targets the CD8 gene in lymphocyte development and interacts with the p53 protein to control genes that are important in proliferation and in the DNA-damage response. PATZ1 exerts its activity through an N-terminal BTB domain that mediates dimerization and co-repressor interactions and a C-terminal zinc-finger motif-containing domain that mediates DNA binding. Here, the crystal structures of the murine and zebrafish PATZ1 BTB domains are reported at 2.3 and 1.8 Å resolution, respectively. The structures revealed that the PATZ1 BTB domain forms a stable homodimer with a lateral surface groove, as in other ZBTB structures. Analysis of the lateral groove revealed a large acidic patch in this region, which contrasts with the previously resolved basic co-repressor binding interface of BCL6. A large 30-amino-acid glycine- and alanine-rich central loop, which is unique to mammalian PATZ1 amongst all ZBTB proteins, could not be resolved, probably owing to its flexibility. Molecular-dynamics simulations suggest a contribution of this loop to modulation of the mammalian BTB dimerization interface.

HBV DNA integrates into upregulated ZBTB20 in patients with hepatocellular carcinoma

Hepatitis B virus (HBV) affects the malignant phenotype of hepatocellular carcinoma (HCC). The aim of the present study was to investigate the integration sites of HBV DNA and the expression of the zinc finger protein, zinc finger and BTB domain containing 20 (ZBTB20) in patients with hepatocellular carcinoma. Integration of the HBV gene was detected using a high-throughput sequencing technique based on the HBV-Alu-PCR method. The expression of ZBTB20 was detected by western blotting. HBVX integration sites were detected in ~70% of the HCC tissue samples. HBV-integrated subgene X detection suggested that 67% of the integrated specimens were inserted into the host X gene in a forward direction, 57% in a reverse direction, 24% in both forward and reverse directions, and 38% had two HBV integration sites. A total of 3,320 HBV integration sites were identified, including 1,397 in HCC tissues, 1,205 in paracancerous tissues and 718 in normal liver tissues. HBV integration fragments displayed enrichment in the 200–800 bp region. Additionally, the results suggested that HBV was highly integrated into transmembrane phosphatase with tensin homology, long intergenic non-protein coding RNA (LINC)00618, LOC101929241, ACTR3 pseudogene 5, LINC00999, LOC101928775, deleted in oesophageal cancer 1, LINC00824, EBF transcription factor 2 and ZBTB20 in tumour tissues. Furthermore, the expression of ZBTB20 was upregulated in HCC tissues compared with normal control liver tissues, and was associated with HBV integration frequency. The present study suggested that HBV DNA integrated into upregulated ZBTB20 in patients with hepatocellular carcinoma, which might promote the occurrence and development of HCC. Furthermore, the results of the present study may provide a theoretical basis for the diagnosis and treatment of HCC.

Plasticity of the Cullin-RING Ligase Repertoire Shapes Sensitivity to Ligand-Induced Protein Degradation

Inducing protein degradation via small molecules is a transformative therapeutic paradigm. Although structural requirements of target degradation are emerging, mechanisms determining the cellular response to small-molecule degraders remain poorly understood. To systematically delineate effectors required for targeted protein degradation, we applied genome-scale CRISPR/Cas9 screens for five drugs that hijack different substrate receptors (SRs) of cullin RING ligases (CRLs) to induce target proteolysis. We found that sensitivity to small-molecule degraders is dictated by shared and drug-specific modulator networks, including the COP9 signalosome and the SR exchange factor CAND1. Genetic or pharmacologic perturbation of these effectors impairs CRL plasticity and arrests a wide array of ligases in a constitutively active state. Resulting defects in CRL decommissioning prompt widespread CRL auto-degradation that confers resistance to multiple degraders. Collectively, our study informs on regulation and architecture of CRLs amenable for targeted protein degradation and outlines biomarkers and putative resistance mechanisms for upcoming clinical investigation.

Identification of ZBTB24 protein domains and motifs for heterochromatin localization and transcriptional activation

Immunodeficiency, centromeric instability, facial anomalies (ICF) syndrome is a rare autosomal recessive disorder caused by mutations in either DNMT3B, ZBTB24, CDCA7, HELLS or an unknown gene(s). Among the known causative genes, ZBTB24 encodes a member of the BTB-zinc finger (ZF) transcription factor family. The protein possesses a BTB domain, an AT-hook and eight C2H2 ZF motifs. All ZBTB24 mutations reported in ICF patients are predicted to disrupt at least one ZF motif. Here, we show that both AT-hook and distinct ZF motifs, particularly the 6th motif, of human and mouse ZBTB24 proteins are important for their heterochromatin localization. On the other hand, the 6th and 7th ZF motifs, and not the AT-hook or the BTB domain, of the human and mouse proteins are essential for transcriptional activation of CDCA7, another ICF causative gene and a known target of ZBTB24. By deletion analysis of the human CDCA7 promoter, we show that two motifs for ZBTB24 binding are important for transcriptional activation of this gene. These results reveal the evolutionarily conserved domains and motifs important for the biological function of ZBTB24, which provides a basis for understanding the molecular mechanisms underlying the pathogenesis of ICF syndrome.

Characterization of the human zinc finger nfx‑1‑type containing 1 encoding ZNFX1 gene and its response to 12‑O‑tetradecanoyl‑13‑acetate in HL‑60 cells

Human promyelocytic HL‑60 cells can be differentiated into macrophage‑like cells by treatment with 12‑O‑tetra decanoylphorbol‑13‑acetate (TPA). Certain 5' upstream regions of the zinc finger protein (ZNF)‑encoding genes contain duplicated GGAA motifs, which are frequently found in the TPA‑responding gene promoter regions. To examine transcriptional responses to TPA, 5'flanking regions of human zinc finger CCCH‑type containing, antiviral, ZNF252, ZNF343, ZNF555, ZNF782 and zinc finger nfx‑1‑type containing 1 (ZNFX1) genes were isolated by polymerase chain reaction (PCR) and ligated into a multiple‑cloning site of the pGL4.10[luc2] vector. Transient transfection and a luciferase assay revealed that the ZNFX1 promoter most prominently responded to the TPA treatment. Deletion and point mutation experiments indicated that the duplicated GGAA motif in the 100‑bp region positively responded to TPA. In addition, reverse transcription‑quantitative PCR and western blotting showed that the mRNA and protein of ZNFX1 accumulate during the differentiation of HL‑60 cells. These results indicated that expression of the TPA‑inducible ZNFX1 gene, which belongs to the group of interferon‑responsive genes, is regulated by the cis‑action of the duplicated GGAA motif.

Progressive Immunodeficiency with Gradual Depletion of B and CD4⁺ T Cells in Immunodeficiency, Centromeric Instability and Facial Anomalies Syndrome 2 (ICF2)

Immunodeficiency, centromeric instability and facial anomalies syndrome 2 (ICF2) is a rare autosomal recessive primary immunodeficiency disorder. So far, 27 patients have been reported. Here, we present three siblings with ICF2 due to a homozygous ZBTB24 gene mutation (c.1222 T>G, p. (Cys408Gly)). Immune deficiency in these patients ranged from late-onset combined immunodeficiency (CID) with severe respiratory tract infections and recurrent shingles to asymptomatic selective antibody deficiency. Evident clinical heterogeneity manifested despite a common genetic background, suggesting the pathogenic relevance of epigenetic modification. Immunological follow-up reveals a previously unidentified gradual depletion of B and CD4⁺ T cells in all three presented patients with transition of a common variable immunodeficiency (CVID)-like disease to late-onset-CID in one of them. Considering all previously published cases with ICF2, we identify inadequate antibody responses to vaccines and reduction in CD27⁺ memory B cells as prevalent immunological traits. High mortality among ICF2 patients (20%) together with the progressive course of immunodeficiency suggest that hematopoietic stem cell transplantation (HSCT) should be considered as a treatment option in due time.

Characterisation of ZBTB46 and DC-SCRIPT/ZNF366 in rainbow trout, transcription factors potentially involved in dendritic cell maturation and activation in fish

ZBTB46 and DC-SCRIPT/ZNF366 are two zinc finger transcription factors that play important roles in regulating differentiation of dendritic cells in mammals. In this study, the ZBTB46 and DC-SCRIPT/ZNF366 homologues were identified in rainbow trout Oncorhynchus mykiss and their expression analysed in vivo and in vitro. As transcription factors, they are well conserved in sequence, genomic organisation and gene synteny. Their expression was differentially modulated by bacterial and viral PAMPs in the monocyte/macrophage-like cell line RTS-11, in primary head kidney (HK) macrophages, and in HK macrophages cultured with IL-4/13A. In the RTS-11 cells and primary HK macrophages, all the ZBTB46 and DC-SCRIPT/ZNF366 homologues were down-regulated by interferon gamma (type II IFN) but unaffected by IFN2 (type I IFN), administered as recombinant proteins to cell cultures. In fish gills, infection with amoebae (Paramoebae perurans) resulted in reduction of ZBTB46 and DC-SCRIPT/ZNF366 expression in Atlantic salmon Salmo salar, whilst infection with Yersinia ruckeri induced gene expression in rainbow trout.

Zbtb1 prevents default myeloid differentiation of lymphoid-primed multipotent progenitors

Zbtb1 is a transcription factor that prevents DNA damage and p53-mediated apoptosis in replicating immune progenitors, affecting lymphoid as well as myeloid development when hematopoietic progenitors are in competition in mixed bone marrow chimeras. However, Zbtb1-deficient mice do not have an apparent myeloid deficiency. We report here that Zbtb1-deficient lymphoid-primed multipotent progenitors (LMPPs) are biased to develop towards the myeloid fate in detriment of lymphoid development, contributing to the apparent unaffected myeloid development. Zbtb1 expression was maintained during lymphoid development of LMPP cells but downregulated during myeloid development. Deficiency of Zbtb1 in LMPP cells was sufficient to direct a myeloid fate in lymphoid-inducing conditions and in the absence of myeloid cytokines as shown by upregulation of a myeloid gene signature and the generation of myeloid cells in vitro. Finally, biased myeloid differentiation of Zbtb1-deficient LMPP cells was not due to increased p53-dependent apoptosis as it was not reverted by transgenic Bcl2 expression or p53 deficiency. Altogether, our results show that Zbtb1 expression prevents activation of a default myeloid program in LMPP cells, ensuring the generation of lymphoid cells.

Zinc Finger-Containing Cellular Transcription Corepressor ZBTB25 Promotes Influenza Virus RNA Transcription and Is a Target for Zinc Ejector Drugs

Influenza A virus (IAV) replication relies on an intricate interaction between virus and host cells. How the cellular proteins are usurped for IAV replication remains largely obscure. The aim of this study was to search for novel and potential cellular factors that participate in IAV replication. ZBTB25, a transcription repressor of a variety of cellular genes, was identified by an RNA interference (RNAi) genomic library screen. Depletion of ZBTB25 significantly reduced IAV production. Conversely, overexpression of ZBTB25 enhanced it. ZBTB25 interacted with the viral RNA-dependent RNA polymerase (RdRp) protein and modulated its transcription activity. In addition, ZBTB25 also functioned as a viral RNA (vRNA)-binding protein, binding preferentially to the U-rich sequence within the 5' untranslated region (UTR) of vRNA. Both protein-protein and protein-RNA interactions involving ZBTB25 facilitated viral RNA transcription and replication. In addition, ZBTB25 suppressed interferon production, further enhancing viral replication. ZBTB25-associated functions required an intact zinc finger domain and posttranslational SUMO-1 modification of ZBTB25. Furthermore, treatment with disulfiram (a zinc ejector) of ZBTB25-overexpressing cells showed significantly reduced IAV production as a result of reduced RNA synthesis. Our findings indicate that IAV usurps ZBTB25 for IAV RNA synthesis and serves as a novel and potential therapeutic antiviral target.IMPORTANCE IAV-induced seasonal influenza causes severe illness and death in high-risk populations. However, IAV has developed resistance to current antiviral drugs due to its high mutation rate. Therefore, development of drugs targeting cellular factors required for IAV replication is an attractive alternative for IAV therapy. Here, we discovered a cellular protein, ZBTB25, that enhances viral RdRp activity by binding to both viral RdRp and viral RNA to stimulate viral RNA synthesis. A unique feature of ZBTB25 in the regulation of viral replication is its dual transcription functions, namely, promoting viral RNA transcription through binding to the U-rich region of vRNA and suppressing cellular interferon production. ZBTB25 contains a zinc finger domain that is required for RNA-inhibitory activity by chelating zinc ions. Disulfiram treatment disrupts the zinc finger functions, effectively repressing IAV replication. Based on our findings, we demonstrate that ZBTB25 regulates IAV RNA transcription and replication and serves as a promising antiviral target for IAV treatment.

The Pu.1 target gene Zbtb11 regulates neutrophil development through its integrase-like HHCC zinc finger

In response to infection and injury, the neutrophil population rapidly expands and then quickly re-establishes the basal state when inflammation resolves. The exact pathways governing neutrophil/macrophage lineage outputs from a common granulocyte-macrophage progenitor are still not completely understood. From a forward genetic screen in zebrafish, we identify the transcriptional repressor, ZBTB11, as critical for basal and emergency granulopoiesis. ZBTB11 sits in a pathway directly downstream of master myeloid regulators including PU.1, and TP53 is one direct ZBTB11 transcriptional target. TP53 repression is dependent on ZBTB11 cys116, which is a functionally critical, metal ion-coordinating residue within a novel viral integrase-like zinc finger domain. To our knowledge, this is the first description of a function for this domain in a cellular protein. We demonstrate that the PU.1–ZBTB11–TP53 pathway is conserved from fish to mammals. Finally, Zbtb11 mutant rescue experiments point to a ZBTB11-regulated TP53 requirement in development of other organs.

Neutrophils are increased in response to injury and infection but how they form from a common granulocyte-macrophage progenitor is unclear. Here, the authors identify a role for the transcriptional repressor ZBTB11 in zebrafish, which is regulated by master myeloid regulators and represses TP53.

Regulation of hematopoietic development by ZBTB transcription factors

Hematopoietic development is governed by the coordinated expression of lineage- and differentiation stage-specific genes. Transcription factors play major roles in this process and their perturbation may underlie hematologic and immunologic disorders. Nearly 1900 transcription factors are encoded in the human genome: of these, 49 BTB (for broad-complex, tram-track and bric à brac)-zinc finger transcription factors referred to as ZBTB or POK proteins have been identified. ZBTB proteins, including BCL6, PLZF, ThPOK and LRF, exhibit a broad spectrum of functions in normal and malignant hematopoiesis. This review summarizes developmental and molecular functions of ZBTB proteins relevant to hematology.

Downregulation of ZBTB24 hampers the G0/1- to S-phase cell-cycle transition via upregulating the expression of IRF-4 in human B cells

It has been recently identified that loss-of-function mutations in the uncharacterized gene ZBTB24 (zinc finger and BTB domain-containing 24) cause ICF2 (immunodeficiency, centromeric instability and facial anomalies syndrome 2) with immunological characteristics of greatly reduced serum antibodies and circulating memory B cells. ZBTB24 belongs to the large ZBTB family of transcriptional repressors with members like B-cell lymphoma 6 (BCL-6; ZBTB27) playing critical roles in B-cell functions. Given the genotype-phenotype correlation analyses in ICF2 patients and the high expression of ZBTB24 in human B cells, we, in the present study, investigated the function of ZBTB24 in human B-cell line Raji cells. Knockdown of endogenous ZBTB24 by small hairpin RNAs results in a significantly reduced proliferation through blocking the G0/1- to S-phase cell-cycle progression, but not apoptosis induction. Moreover, downregulation of ZBTB24 increases the expression of IRF-4 (interferon regulatory factor 4) and Blimp-1 (B lymphocyte-induced maturation protein 1), two crucial factors involved in the proliferation and differentiation of B cells. Importantly, ZBTB24 exerts these functions independent of BCL-6 as it does not affect the expression and function of BCL-6. Our study thus not only provides a molecular explanation for the B-cell and antibody defects observed in ZBTB24-deficient ICF2 patients, but also indicates that ZBTB24 represents a novel transcriptional factor essentially involved in human B-cell functions.

A Temporal Switch in the Germinal Center Determines Differential Output of Memory B and Plasma Cells

There is little insight into or agreement about the signals that control differentiation of memory B cells (MBCs) and long-lived plasma cells (LLPCs). By performing BrdU pulse-labeling studies, we found that MBC formation preceded the formation of LLPCs in an adoptive transfer immunization system, which allowed for a synchronized Ag-specific response with homogeneous Ag-receptor, yet at natural precursor frequencies. We confirmed these observations in wild-type (WT) mice and extended them with germinal center (GC) disruption experiments and variable region gene sequencing. We thus show that the GC response undergoes a temporal switch in its output as it matures, revealing that the reaction engenders both MBC subsets with different immune effector function and, ultimately, LLPCs at largely separate points in time. These data demonstrate the kinetics of the formation of the cells that provide stable humoral immunity and therefore have implications for autoimmunity, for vaccine development, and for understanding long-term pathogen resistance.

The BTB-ZF transcription factor Zbtb20 is driven by Irf4 to promote plasma cell differentiation and longevity

Zbtb20 facilitates terminal differentiation of B cells into antibody-secreting cells, and its expression is dependent on Irf4 and independent of Blimp1.

The transcriptional network regulating antibody-secreting cell (ASC) differentiation has been extensively studied, but our current understanding is limited. The mechanisms of action of known “master” regulators are still unclear, while the participation of new factors is being revealed. Here, we identify Zbtb20, a Bcl6 homologue, as a novel regulator of late B cell development. Within the B cell lineage, Zbtb20 is specifically expressed in B1 and germinal center B cells and peaks in long-lived bone marrow (BM) ASCs. Unlike Bcl6, an inhibitor of ASC differentiation, ectopic Zbtb20 expression in primary B cells facilitates terminal B cell differentiation to ASCs. In plasma cell lines, Zbtb20 induces cell survival and blocks cell cycle progression. Immunized Zbtb20-deficient mice exhibit curtailed humoral responses and accelerated loss of antigen-specific plasma cells, specifically from the BM pool. Strikingly, Zbtb20 induction does not require Blimp1 but depends directly on Irf4, acting at a newly identified Zbtb20 promoter in ASCs. These results identify Zbtb20 as an important player in late B cell differentiation and provide new insights into this complex process.