Plzf mediates transcriptional repression of HoxD gene expression through chromatin remodeling

ZBTB16 inhibits DNA replication and induces cell cycle arrest by targeting WDHD1 transcription in lung adenocarcinoma

Lung adenocarcinoma is a malignant tumor with high morbidity and mortality. ZBTB16 plays a double role in various tumors; however, the potential mechanism of ZBTB16 in the pathophysiology of lung adenocarcinoma has yet to be elucidated. We herein observed a decreased expression of ZBTB16 mRNA and protein in lung adenocarcinoma and a significantly increased DNA methylation level of ZBTB16 in patients with lung adenocarcinoma. Analysis of public databases and patients' clinical data indicated a close association between ZBTB16 and patient survival. Ectopic expression of ZBTB16 in lung adenocarcinoma cells significantly inhibited cell proliferation, invasion, and migration. It also induced cell cycle arrest in the S phase. Meanwhile, mitotic catastrophe was induced, and DNA damage and apoptosis occurred. In line with these findings, the overexpression of ZBTB16 in xenograft mice resulted in the inhibition of tumor growth. Comprehensive analysis showed that WDHD1 was a potential target for ZBTB16. The overexpression of both isoforms of WDHD1 significantly reversed the ZBTB16-mediated inhibition of lung adenocarcinoma proliferation and cell cycle. These studies suggest that ZBTB16 impedes the progression of lung adenocarcinoma by interfering with WDHD1 transcription, making it a potential novel therapeutic target in the management of lung adenocarcinoma.

Glucocorticoid receptor-mediated oncogenic activity is dependent on breast cancer subtype

Breast cancer incidence has been steadily rising and is the leading cause of cancer death in women due to its high metastatic potential. Individual breast cancer subtypes are classified by both cell type of origin and receptor expression, namely estrogen, progesterone and human epidermal growth factor receptors (ER, PR and HER2). Recently, the importance and context-dependent role of glucocorticoid receptor (GR) expression in the natural history and prognosis of breast cancer subtypes has been uncovered. In ER-positive breast cancer, GR expression is associated with a better prognosis as a result of ER-GR crosstalk. GR appears to modulate ER-mediated gene expression resulting in decreased tumor cell proliferation and a more indolent cancer phenotype. In ER-negative breast cancer, including GR-positive triple-negative breast cancer (TNBC), GR expression enhances migration, chemotherapy resistance and cell survival. In invasive lobular carcinoma, GR function is relatively understudied, and more work is required to determine whether lobular subtypes behave similarly to their invasive ductal carcinoma counterparts. Importantly, understanding GR signaling in individual breast cancer subtypes has potential clinical implications because of the recent development of highly selective GR non-steroidal ligands, which represent a therapeutic approach for modulating GR activity systemically.

Luminal breast cancer identity is determined by loss of glucocorticoid receptor activity

Glucocorticoid receptor (GR) is a transcription factor that plays a crucial role in cancer biology. In this study, we utilized an in silico-designed GR activity signature to demonstrate that GR relates to the proliferative capacity of numerous primary cancer types. In breast cancer, the GR activity status determines luminal subtype identity and has implications for patient outcomes. We reveal that GR engages with estrogen receptor (ER), leading to redistribution of ER on the chromatin. Notably, GR activation leads to upregulation of the ZBTB16 gene, encoding for a transcriptional repressor, which controls growth in ER-positive breast cancer and associates with prognosis in luminal A patients. In relation to ZBTB16's repressive nature, GR activation leads to epigenetic remodeling and loss of histone acetylation at sites proximal to cancer-driving genes. Based on these findings, epigenetic inhibitors reduce viability of ER-positive breast cancer cells that display absence of GR activity. Our findings provide insights into how GR controls ER-positive breast cancer growth and may have implications for patients' prognostication and provide novel therapeutic candidates for breast cancer treatment.

Unaltered hepatic wound healing response in male rats with ancestral liver injury

The possibility that ancestral environmental exposure could result in adaptive inherited effects in mammals has been long debated. Numerous rodent models of transgenerational responses to various environmental factors have been published but due to technical, operational and resource burden, most still await independent confirmation. A previous study reported multigenerational epigenetic adaptation of the hepatic wound healing response upon exposure to the hepatotoxicant carbon tetrachloride (CCl4) in male rats. Here, we comprehensively investigate the transgenerational effects by repeating the original CCl4 multigenerational study with increased power, pedigree tracing, F2 dose-response and suitable randomization schemes. Detailed pathology evaluations do not support adaptive phenotypic suppression of the hepatic wound healing response or a greater fitness of F2 animals with ancestral liver injury exposure. However, transcriptomic analyses identified genes whose expression correlates with ancestral liver injury, although the biological relevance of this apparent transgenerational transmission at the molecular level remains to be determined. This work overall highlights the need for independent evaluation of transgenerational epigenetic inheritance paradigms in mammals.

Enhanced ZBTB16 Levels by Progestin-Only Contraceptives Induces Decidualization and Inflammation

Progestin-only long-acting reversible-contraceptive (pLARC)-exposed endometria displays decidualized human endometrial stromal cells (HESCs) and hyperdilated thin-walled fragile microvessels. The combination of fragile microvessels and enhanced tissue factor levels in decidualized HESCs generates excess thrombin, which contributes to abnormal uterine bleeding (AUB) by inducing inflammation, aberrant angiogenesis, and proteolysis. The- zinc finger and BTB domain containing 16 (ZBTB16) has been reported as an essential regulator of decidualization. Microarray studies have demonstrated that ZBTB16 levels are induced by medroxyprogesterone acetate (MPA) and etonogestrel (ETO) in cultured HESCs. We hypothesized that pLARC-induced ZBTB16 expression contributes to HESC decidualization, whereas prolonged enhancement of ZBTB16 levels triggers an inflammatory milieu by inducing pro-inflammatory gene expression and tissue-factor-mediated thrombin generation in decidualized HESCs. Thus, ZBTB16 immunostaining was performed in paired endometria from pre- and post-depo-MPA (DMPA)-administrated women and oophorectomized guinea pigs exposed to the vehicle, estradiol (E₂), MPA, or E₂ + MPA. The effect of progestins including MPA, ETO, and levonorgestrel (LNG) and estradiol + MPA + cyclic-AMP (E₂ + MPA + cAMP) on ZBTB16 levels were measured in HESC cultures by qPCR and immunoblotting. The regulation of ZBTB16 levels by MPA was evaluated in glucocorticoid-receptor-silenced HESC cultures. ZBTB16 was overexpressed in cultured HESCs for 72 h followed by a ± 1 IU/mL thrombin treatment for 6 h. DMPA administration in women and MPA treatment in guinea pigs enhanced ZBTB16 immunostaining in endometrial stromal and glandular epithelial cells. The in vitro findings indicated that: (1) ZBTB16 levels were significantly elevated by all progestin treatments; (2) MPA exerted the greatest effect on ZBTB16 levels; (3) MPA-induced ZBTB16 expression was inhibited in glucocorticoid-receptor-silenced HESCs. Moreover, ZBTB16 overexpression in HESCs significantly enhanced prolactin (PRL), insulin-like growth factor binding protein 1 (IGFBP1), and tissue factor (F3) levels. Thrombin-induced interleukin 8 (IL-8) and prostaglandin-endoperoxide synthase 2 (PTGS2) mRNA levels in control-vector-transfected HESCs were further increased by ZBTB16 overexpression. In conclusion, these results supported that ZBTB16 is enhanced during decidualization, and long-term induction of ZBTB16 expression by pLARCs contributes to thrombin generation through enhancing tissue factor expression and inflammation by enhancing IL-8 and PTGS2 levels in decidualized HESCs.

PLZF Acetylation Levels Regulate NKT Cell Differentiation

The transcription factor promyelocytic leukemia zinc finger (PLZF) is encoded by the BTB domain-containing 16 (Zbtb16) gene. Its repressor function regulates specific transcriptional programs. During the development of invariant NKT cells, PLZF is expressed and directs their effector program, but the detailed mechanisms underlying PLZF regulation of multistage NKT cell developmental program are not well understood. This study investigated the role of acetylation-induced PLZF activation on NKT cell development by analyzing mice expressing a mutant form of PLZF mimicking constitutive acetylation (PLZF^ON) mice. NKT populations in PLZF^ON mice were reduced in proportion and numbers of cells, and the cells present were blocked at the transition from developmental stage 1 to stage 2. NKT cell subset differentiation was also altered, with T-bet⁺ NKT1 and RORγt⁺ NKT17 subsets dramatically reduced and the emergence of a T-bet^-RORγt^- NKT cell subset with features of cells in early developmental stages rather than mature NKT2 cells. Preliminary analysis of DNA methylation patterns suggested that activated PLZF acts on the DNA methylation signature to regulate NKT cells' entry into the early stages of development while repressing maturation. In wild-type NKT cells, deacetylation of PLZF is possible, allowing subsequent NKT cell differentiation. Interestingly, development of other innate lymphoid and myeloid cells that are dependent on PLZF for their generation is not altered in PLZF^ON mice, highlighting lineage-specific regulation. Overall, we propose that specific epigenetic control of PLZF through acetylation levels is required to regulate normal NKT cell differentiation.

NLRP7: From inflammasome regulation to human disease

Nucleotide-binding oligomerization domain (NOD) and leucine-rich repeat (LRR)-containing receptors or NOD-like receptors (NLRs) are cytosolic pattern recognition receptors, which sense conserved microbial patterns and host-derived danger signals to elicit innate immune responses. The activation of several prototypic NLRs, including NLR and pyrin domain (PYD) containing (NLRP) 1, NLRP3 and NLR and caspase recruitment domain (CARD) containing (NLRC) 4, results in the assembly of inflammasomes, which are large, cytoplasmic multiprotein signalling platforms responsible for the maturation and release of the pro-inflammatory cytokines IL-1β and IL-18, and for the induction of a specialized form of inflammatory cell death called pyroptosis. However, the function of other members of the NLR family, including NLRP7, are less well understood. NLRP7 has been linked to innate immune signalling, but its precise role is still controversial as it has been shown to positively and negatively affect inflammasome responses. Inflammasomes are essential for homeostasis and host defence, but inappropriate inflammasome responses due to hereditary mutations and somatic mosaicism in inflammasome components and defective regulation have been linked to a broad spectrum of human diseases. A compelling connection between NLRP7 mutations and reproductive diseases, and in particular molar pregnancy, has been established. However, the molecular mechanisms by which NLRP7 mutations contribute to reproductive diseases are largely unknown. In this review, we focus on NLRP7 and discuss the current evidence of its role in inflammasome regulation and its implication in human reproductive diseases.

Quantitative Difference in PLZF Protein Expression Determines iNKT Lineage Fate and Controls Innate CD8 T Cell Generation

Zbtb16 encodes the zinc-finger protein PLZF, which is often used as a lineage marker for innate-like T cells and is specifically required for the generation of invariant natural killer T (iNKT) cells in the thymus. Here, we report that not only PLZF expression itself but also the relative abundance of PLZF proteins plays critical roles in iNKT cell development. Utilizing a Zbtb16 hypomorphic allele, PLZF^GFPCre, which produces PLZF proteins at only half of the level of the wild-type allele, we show that decreased PLZF expression results in a significant decrease in iNKT cell numbers, which is further associated with profound alterations in iNKT lineage choices and subset composition. These results document that there is a quantitative aspect of PLZF expression in iNKT cells, demonstrating that the availability of PLZF protein is a critical factor for both effective iNKT cell generation and subset differentiation.

Survival Motor Neuron Protein Participates in Mouse Germ Cell Development and Spermatogonium Maintenance

The defective human survival motor neuron 1 (SMN1) gene leads to spinal muscular atrophy (SMA), the most common genetic cause of infant mortality. We previously reported that loss of SMN results in rapid differentiation of Drosophila germline stem cells and mouse embryonic stem cells (ESCs), indicating that SMN also plays important roles in germ cell development and stem cell biology. Here, we show that in healthy mice, SMN is highly expressed in the gonadal tissues, prepubertal spermatogonia, and adult spermatocytes, whereas low SMN expression is found in differentiated spermatid and sperm. In SMA-like mice, the growth of testis tissues is retarded, accompanied with gamete development abnormalities and loss of the spermatogonia-specific marker. Consistently, knockdown of Smn1 in spermatogonial stem cells (SSCs) leads to a compromised regeneration capacity in vitro and in vivo in transplantation experiments. In SMA-like mice, apoptosis and accumulation of the R-loop structure were significantly elevated, indicating that SMN plays a critical role in the survival of male germ cells. The present work demonstrates that SMN, in addition to its critical roles in neuronal development, participates in mouse germ cell and spermatogonium maintenance.

Advances of Zinc Signaling Studies in Prostate Cancer

Prostate cancer (PCa) is one of the most common cancers and the second leading cause of cancer-related death among men worldwide. Despite progresses in early diagnosis and therapeutic strategies, prognosis for patients with advanced PCa remains poor. Noteworthily, a unique feature of healthy prostate is its highest level of zinc content among all soft tissues in the human body, which dramatically decreases during prostate tumorigenesis. To date, several reviews have suggested antitumor activities of zinc and its potential as a therapeutic strategy of PCa. However, an overview about the role of zinc and its signaling in PCa is needed. Here, we review literature related to the content, biological function, compounds and clinical application of zinc in PCa. We first summarize zinc content in prostate tissue and sera of PCa patients with their clinical relevance. We then elaborate biological functions of zinc signaling in PCa on three main aspects, including cell proliferation, death and tumor metastasis. Finally, we discuss clinical applications of zinc-containing compounds and proteins involved in PCa signaling pathways. Based on currently available studies, we conclude that zinc plays a tumor suppressive role and can serve as a biomarker in PCa diagnosis and therapies.

PLZF limits enhancer activity during hematopoietic progenitor aging

PLZF (promyelocytic leukemia zinc finger) is a transcription factor acting as a global regulator of hematopoietic commitment. PLZF displays an epigenetic specificity by recruiting chromatin-modifying factors but little is known about its role in remodeling chromatin of cells committed toward a given specific hematopoietic lineage. In murine myeloid progenitors, we decipher a new role for PLZF in restraining active genes and enhancers by targeting acetylated lysine 27 of Histone H3 (H3K27ac). Functional analyses reveal that active enhancers bound by PLZF are involved in biological processes related to metabolism and associated with hematopoietic aging. Comparing the epigenome of young and old myeloid progenitors, we reveal that H3K27ac variation at active enhancers is a hallmark of hematopoietic aging. Taken together, these data suggest that PLZF, associated with active enhancers, appears to restrain their activity as an epigenetic gatekeeper of hematopoietic aging.

PLZF suppresses differentiation of mouse spermatogonial progenitor cells via binding of differentiation associated genes

Promyelocytic leukaemia zinc finger (PLZF) is a key factor in inhibiting differentiation of spermatogonial progenitor cells (SPCs), but the underlying mechanisms are still largely unknown. In this study, the regulation of PLZF on Kit, Stra8, Sohlh2, and Dmrt1 (SPCs differentiation related genes) was investigated. We found some PLZF potential binding sites existed in the promoters of Kit, Stra8, Sohlh2, and Dmrt1. Additionally, the expressions of KIT, STRA8, SOHLH2, and DMRT1 were upregulated when PLZF was knockdown in SPCs. Furthermore, chromatin immunoprecipitation quantitative polymerase chain reaction revealed PLZF directly bound to the promoters of Kit, Stra8, Sohlh2, and Dmrt1. Besides, dual luciferase assay verified PLZF repressed those gene expressions. Collectively, our finding indicate that PLZF binds to the promoter regions of Kit, Stra8, Sohlh2, and Dmrt1 to regulate SPCs differentiation, which facilitate us to further understand the regulatory mechanism of PLZF in SPCs fates.

Regulation of the positive transcriptional effect of PLZF through a non-canonical EZH2 activity

The transcription factor PLZF (promyelocytic leukemia zinc finger protein) acts as an epigenetic regulator balancing self-renewal and differentiation of hematopoietic cells through binding to various chromatin-modifying factors. First described as a transcriptional repressor, PLZF is also associated with active transcription, although the molecular bases underlying the differences are unknown. Here, we reveal that in a hematopoietic cell line, PLZF is predominantly associated with transcribed genes. Additionally, we identify a new association between PLZF and the histone methyltransferase, EZH2 at the genomic level. We find that co-occupancy of PLZF and EZH2 on chromatin at PLZF target genes is not associated with SUZ12 or trimethylated lysine 27 of histone H3 (H3K27me3) but with the active histone mark H3K4me3 and active transcription. Removal of EZH2 leads to an increase of PLZF binding and increased gene expression. Our results suggest a new role of EZH2 in restricting PLZF positive transcriptional activity independently of its canonical PRC2 activity.

Eicosanoids and HB-EGF/EGFR in cancer

Eicosanoids are bioactive lipids that play crucial roles in various pathophysiological conditions, including inflammation and cancer. They include both the COX-derived prostaglandins and the LOX-derived leukotrienes. Furthermore, the epidermal growth factor receptor (EGFR) pathways family of receptor tyrosine kinases also are known to play a central role in the tumorigenesis. Various antitumor modalities have been approved cancer treatments that target therapeutically the COX-2 and EGFR pathways; these include selective COX-2 inhibitors and EGFR monoclonal antibodies. Research has shown that the COX-2 and epidermal growth factor receptor pathways actively interact with each other in order to orchestrate carcinogenesis. This has been used to justify a targeted combinatorial approach aimed at these two pathways. Although combined therapies have been found to have a greater antitumor effect than the administration of single agent, this does not exempt them from the possible fatal cardiac effects that are associated with COX-2 inhibition. In this review, we delineate the contribution of HB-EGF, an important EGFR ligand, to the cardiac dysfunction related to decreased shedding of HB-EGF after COX-2/PGE2 inhibition. A better understanding of the molecular mechanisms underlying these cardiac side effects will make possible more effective regimens that use the dual-targeting approach.

RETRACTED: Function of the PLZF gene in early development and self-renewal of T cells in mice

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal).. This article has been retracted at the request of < the Editor in Chief. The Editor in Chief has been made aware of numerous problems with this paper regarding authorship, poor or insufficient supervision of researchers and the unauthorized use of data acquired from a lab visit by one of the authors.

PLZF targets developmental enhancers for activation during osteogenic differentiation of human mesenchymal stem cells

The PLZF transcription factor is essential for osteogenic differentiation of hMSCs; however, its regulation and molecular function during this process is not fully understood. Here, we revealed that the ZBTB16 locus encoding PLZF, is repressed by Polycomb (PcG) and H3K27me3 in naive hMSCs. At the pre-osteoblast stage of differentiation, the locus lost PcG binding and H3K27me3, gained JMJD3 recruitment, and H3K27ac resulting in high expression of PLZF. Subsequently, PLZF was recruited to osteogenic enhancers, influencing H3K27 acetylation and expression of nearby genes important for osteogenic function. Furthermore, we identified a latent enhancer within the ZBTB16/PLZF locus itself that became active, gained PLZF, p300 and Mediator binding and looped to the promoter of the nicotinamide N-methyltransferase (NNMT) gene. The increased expression of NNMT correlated with a decline in SAM levels, which is dependent on PLZF and is required for osteogenic differentiation.

Primordial follicle activation is affected by the absence of Sohlh1 in mice

Previous studies have reported that only primordial follicles and empty follicles can be found in 7.5 days postparturition (dpp) Sohlh1^-/- mouse ovaries and females are infertility. There appears to be a defect in follicle development during the primordial-to-primary follicle transition in Sohlh1^-/- mouse ovaries. However, detailed analyses of these phenomena have not been performed. In this study, we used Sohlh1^-/- transgenic mice to explore the role of Sohlh1 in folliculogenesis. The results showed that only primordial follicles and empty follicles can be observed in Sohlh1^-/- ovaries from 0.5 to 23.5 dpp. The expression of Foxo3 and FOXO3 was downregulated; nucleocytoplasmic shuttling of FOXO3 was normal in 7.5-dpp Sohlh1^+/+ but not Sohlh1^-/- ovaries; and primordial follicle activation (PFA) was not observed in 7.5-dpp Sohlh1^-/- mice. The expression levels of KIT, AKT, and P308-AKT were downregulated (p < 0.05), whereas that of P473-AKT was not significantly changed (p > 0.05). The KIT/PI3K/AKT pathway was inhibited. Furthermore, we conducted a dual luciferase assay and chromatin immunoprecipitation. The results showed that SOHLH1 can upregulate the Kit gene by binding to the -3698 bp E-box motif. The absence of Sohlh1 may affect PFA in mouse ovaries via downregulation of Kit and inhibition of the KIT/PI3K/AKT pathway.

ZBTB16 and metabolic syndrome: a network perspective

Metabolic syndrome is a prevalent, complex condition. The search for genetic determinants of the syndrome is currently undergoing a paradigm enhancement by adding systems genetics approaches to association studies. We summarize the current evidence on relations between an emergent new candidate, zinc finger and BTB domain containing 16 (ZBTB16) transcription factor and the major components constituting the metabolic syndrome. Information stemming from studies on experimental models with altered Zbtb16 expression clearly shows its effect on adipogenesis, cardiac hypertrophy and fibrosis, lipid levels and insulin sensitivity. Based on current evidence, we provide a network view of relations between ZBTB16 and hallmarks of metabolic syndrome in order to elucidate the potential functional links involving the ZBTB16 node. Many of the identified genes interconnecting ZBTB16 with all or most metabolic syndrome components are linked to immune function, inflammation or oxidative stress. In summary, ZBTB16 represents a promising pleiotropic candidate node for metabolic syndrome.

Genetic interaction between Gli3 and Ezh2 during limb pattern formation

Anteroposterior polarity of the early limb bud is essential for proper skeletal pattern formation. In order to establish anterior identity, hedgehog signalling needs to be repressed by GLI3 repressor activity, although the mechanism of repression is not well defined. Here we describe genetic interaction between Gli3 and Enhancer of Zeste 2 (Ezh2) that encodes the histone methyltransferase subunit of Polycomb Repressive Complex 2. Loss of anterior limb identity was evident in both Gli3 and conditional Ezh2 single mutant embryos. This phenotype was enhanced in Ezh2;Gli3 double mutant embryos, but more closely resembled that of Ezh2 single mutants. Absent anterior skeletal elements in the Ezh2 mutant background were not rescued by either reduction of Gli activator or forced expression of Gli repressor. The data imply that Ezh2 is epistatic to Gli3 and suggest the possibility that hedghehog activation is repressed by the recruitment of polycomb repressive complex 2.

Role of PLZF as a tumor suppressor in prostate cancer

The promyelocytic leukemia zinc finger (PLZF), also known as ZBTB16 (Zinc Finger And BTB Domain Containing 16), is a transcription factor involved in the regulation of diverse biological processes, including cell proliferation, differentiation, organ development, stem cell maintenance and innate immune cell development. A number of recent studies have now implicated PLZF in cancer progression as a tumor suppressor. However, in certain cancer types, PLZF may function as an oncoprotein. Here, we summarize our current knowledge on the role of PLZF in various cancer types, in particular prostate cancer, including its deregulation, genomic alterations and potential functions in prostate cancer progression.

Eya2, a Target Activated by Plzf, Is Critical for PLZF-RARA-Induced Leukemogenesis

PLZF is a transcription factor that confers aberrant self-renewal in leukemogenesis, and the PLZF-RARA fusion gene causes acute promyelocytic leukemia (APL) through differentiation block. However, the molecular mechanisms of aberrant self-renewal underlying PLZF-mediated leukemogenesis are poorly understood. To investigate these mechanisms, comprehensive expression profiling of mouse hematopoietic stem/progenitor cells transduced with Plzf was performed, which revealed the involvement of a key transcriptional coactivator, Eya2, a target molecule shared by Plzf and PLZF-RARA, in the aberrant self-renewal. Indeed, PLZF-RARA as well as Plzf rendered those cells immortalized through upregulation of Eya2. Eya2 also led to immortalization without differentiation block, while depletion of Eya2 suppressed clonogenicity in cells immortalized by PLZF-RARA without influence on differentiation and apoptosis. Interestingly, cancer outlier profile analysis of human samples of acute myeloid leukemia (AML) in The Cancer Genome Atlas (TCGA) revealed a subtype of AML that strongly expressed EYA2 In addition, gene set enrichment analysis of human AML samples, including TCGA data, showed that this subtype of AML was more closely associated with the properties of leukemic stem cells in its gene expression signature than other AMLs. Therefore, EYA2 may be a target for molecular therapy in this subtype of AML, including PLZF-RARA APL.

Compositional and functional diversity of canonical PRC1 complexes in mammals

The compositional complexity of Polycomb Repressive Complex 1 (PRC1) increased dramatically during vertebrate evolution. What is considered the "canonical" PRC1 complex consists of four subunits originally identified as regulators of body segmentation in Drosophila. In mammals, each of these four canonical subunits consists of two to six paralogs that associate in a combinatorial manner to produce over a hundred possible distinct PRC1 complexes with unknown function. Genetic studies have begun to define the phenotypic roles for different PRC1 paralogs; however, relating these phenotypes to unique biochemical and transcriptional function for the different paralogs has been challenging. In this review, we attempt to address how the compositional diversity of canonical PRC1 complexes relates to unique roles for individual PRC1 paralogs in transcriptional regulation. This review focuses primarily on PRC1 complex composition, genome targeting, and biochemical function.

An Integrative Analysis of Preeclampsia Based on the Construction of an Extended Composite Network Featuring Protein-Protein Physical Interactions and Transcriptional Relationships

Preeclampsia (PE) is a pregnancy disorder defined by hypertension and proteinuria. This disease remains a major cause of maternal and fetal morbidity and mortality. Defective placentation is generally described as being at the root of the disease. The characterization of the transcriptome signature of the preeclamptic placenta has allowed to identify differentially expressed genes (DEGs). However, we still lack a detailed knowledge on how these DEGs impact the function of the placenta. The tools of network biology offer a methodology to explore complex diseases at a systems level. In this study we performed a cross-platform meta-analysis of seven publically available gene expression datasets comparing non-pathological and preeclamptic placentas. Using the rank product algorithm we identified a total of 369 DEGs consistently modified in PE. The DEGs were used as seeds to build both an extended physical protein-protein interactions network and a transcription factors regulatory network. Topological and clustering analysis was conducted to analyze the connectivity properties of the networks. Finally both networks were merged into a composite network which presents an integrated view of the regulatory pathways involved in preeclampsia and the crosstalk between them. This network is a useful tool to explore the relationship between the DEGs and enable hypothesis generation for functional experimentation.

Identification of Novel EZH2 Targets Regulating Osteogenic Differentiation in Mesenchymal Stem Cells

Histone three lysine 27 (H3K27) methyltransferase enhancer of zeste homolog 2 (EZH2) is a critical epigenetic modifier, which regulates gene transcription through the trimethylation of the H3K27 residue leading to chromatin compaction and gene repression. EZH2 has previously been identified to regulate human bone marrow-derived mesenchymal stem cells (MSC) lineage specification. MSC lineage specification is regulated by the presence of EZH2 and its H3K27me3 modification or the removal of the H3K27 modification by lysine demethylases 6A and 6B (KDM6A and KDM6B). This study used a bioinformatics approach to identify novel genes regulated by EZH2 during MSC osteogenic differentiation. In this study, we identified the EZH2 targets, ZBTB16, MX1, and FHL1, which were expressed at low levels in MSC. EZH2 and H3K27me3 were found to be present along the transcription start site of their respective promoters. During osteogenesis, these genes become actively expressed coinciding with the disappearance of EZH2 and H3K27me3 on the transcription start site of these genes and the enrichment of the active H3K4me3 modification. Overexpression of EZH2 downregulated the transcript levels of ZBTB16, MX1, and FHL1 during osteogenesis. Small interfering RNA targeting of MX1 and FHL1 was associated with a downregulation of the key osteogenic transcription factor, RUNX2, and its downstream targets osteopontin and osteocalcin. These findings highlight that EZH2 not only acts through the direct regulation of signaling modules and lineage-specific transcription factors but also targets many novel genes important for mediating MSC osteogenic differentiation.

The Promyelocytic Leukemia Zinc Finger Transcription Factor Is Critical for Human Endometrial Stromal Cell Decidualization

Progesterone, via the progesterone receptor (PGR), is essential for endometrial stromal cell decidualization, a cellular transformation event in which stromal fibroblasts differentiate into decidual cells. Uterine decidualization supports embryo implantation and placentation as well as subsequent events, which together ensure a successful pregnancy. Accordingly, impaired decidualization results not only in implantation failure or early fetal miscarriage, but also may lead to potential adverse outcomes in all three pregnancy trimesters. Transcriptional reprogramming on a genome-wide scale underlies progesterone dependent decidualization of the human endometrial stromal cell (hESC). However, identification of the functionally essential signals encoded by these global transcriptional changes remains incomplete. Importantly, this knowledge-gap undercuts future efforts to improve diagnosis and treatment of implantation failure based on a dysfunctional endometrium. By integrating genome-wide datasets derived from decidualization of hESCs in culture, we reveal that the promyelocytic leukemia zinc finger (PLZF) transcription factor is rapidly induced by progesterone and that this induction is indispensable for progesterone-dependent decidualization. Chromatin immunoprecipitation followed by next generation sequencing (ChIP-Seq) identified at least ten progesterone response elements within the PLZF gene, indicating that PLZF may act as a direct target of PGR signaling. The spatiotemporal expression profile for PLZF in both the human and mouse endometrium offers further support for stromal PLZF as a mediator of the progesterone decidual signal. To identify functional targets of PLZF, integration of PLZF ChIP-Seq and RNA Pol II RNA-Seq datasets revealed that the early growth response 1 (EGR1) transcription factor is a PLZF target for which its level of expression must be reduced to enable progesterone dependent hESC decidualization. Apart from furnishing essential insights into the molecular mechanisms by which progesterone drives hESC decidualization, our findings provide a new conceptual framework that could lead to new avenues for diagnosis and/or treatment of adverse reproductive outcomes associated with a dysfunctional uterus.

PLZF mutation alters mouse hematopoietic stem cell function and cell cycle progression

Hematopoietic stem cells (HSCs) give rise to all blood populations due to their long-term self-renewal and multipotent differentiation capacities. Because they have to persist throughout an organism's life span, HSCs tightly regulate the balance between proliferation and quiescence. Here, we investigated the role of the transcription factor promyelocytic leukemia zinc finger (plzf) in HSC fate using the Zbtb16(lu/lu)mouse model, which harbors a natural spontaneous mutation that inactivates plzf. Regenerative stress revealed that Zbtb16(lu/lu)HSCs had a lineage-skewing potential from lymphopoiesis toward myelopoiesis, an increase in the long-term-HSC pool, and a decreased repopulation potential. Furthermore, oldplzf-mutant HSCs present an amplified aging phenotype, suggesting that plzf controls age-related pathway. We found that Zbtb16(lu/lu)HSCs harbor a transcriptional signature associated with a loss of stemness and cell cycle deregulation. Lastly, cell cycle analyses revealed an important role for plzf in the regulation of the G1-S transition of HSCs. Our study reveals a new role for plzf in regulating HSC function that is linked to cell cycle regulation, and positions plzf as a key player in controlling HSC homeostasis.

The dynamic genome: transposons and environmental adaptation in the nervous system

Classically thought as genomic clutter, the functional significance of transposable elements (TEs) has only recently become a focus of attention in neuroscience. Increasingly, studies have demonstrated that the brain seems to have more retrotransposition and TE transcription relative to other somatic tissues, suggesting a unique role for TEs in the central nervous system. TE expression and transposition also appear to vary by brain region and change in response to environmental stimuli such as stress. TEs appear to serve a number of adaptive roles in the nervous system. The regulation of TE expression by steroid, epigenetic and other mechanisms in interplay with the environment represents a significant and novel avenue to understanding both normal brain function and disease.

NLRP7, Involved in Hydatidiform Molar Pregnancy (HYDM1), Interacts with the Transcriptional Repressor ZBTB16

Mutations in the maternal effect gene NLRP7 cause biparental hydatidiform mole (HYDM1). HYDM1 is characterized by abnormal growth of placenta and lack of proper embryonic development. The molar tissues are characterized by abnormal methylation patterns at differentially methylated regions (DMRs) of imprinted genes. It is not known whether this occurs before or after fertilization, but the high specificity of this defect to the maternal allele indicates a possible maternal germ line-specific effect. To better understand the unknown molecular mechanism leading to HYDM1, we performed a yeast two-hybrid screen against an ovarian library using NLRP7 as bait. We identified the transcriptional repressor ZBTB16 as an interacting protein of NLRP7 and verified this interaction in mammalian cells by immunoprecipitation and confocal microscopy. Native protein analysis detected NLRP7 and ZBTB16 in a 480kD protein complex and both proteins co-localize in the cytoplasm in juxtanuclear aggregates. HYDM1-causing mutations in NLRP7 did not show altered patterns of interaction with ZBTB16. Hence, the biological significance of the NLRP7-ZBTB16 interaction remains to be revealed. However, a clear effect of harvesting ZBTB16 to the cytoplasm when the NLRP7 protein is overexpressed may be linked to the pathology of the molar pregnancy disease.

Genetic-epigenetic dysregulation of thymic TSH receptor gene expression triggers thyroid autoimmunity

Graves disease (GD) is an autoimmune condition caused by interacting genetic and environmental factors. Genetic studies have mapped several single-nucleotide polymorphisms (SNPs) that are strongly associated with GD, but the mechanisms by which they trigger disease are unknown. We hypothesized that epigenetic modifications induced by microenvironmental influences of cytokines can reveal the functionality of GD-associated SNPs. We analyzed genome-wide histone H3 lysine 4 methylation and gene expression in thyroid cells induced by IFNα, a key cytokine secreted during viral infections, and overlapped them with known GD-associated SNPs. We mapped an open chromatin region overlapping two adjacent GD-associated SNPs (rs12101255 and rs12101261) in intron 1 of the thyroid stimulating hormone receptor (TSHR) gene. We then demonstrated that this region functions as a regulatory element through binding of the transcriptional repressor promyelocytic leukemia zinc finger protein (PLZF) at the rs12101261 site. Repression by PLZF depended on the rs12101261 disease susceptibility allele and was increased by IFNα. Intrathymic TSHR expression was decreased in individuals homozygous for the rs12101261 disease-associated genotype compared with carriers of the disease-protective allele. Our studies discovered a genetic-epigenetic interaction involving a noncoding SNP in the TSHR gene that regulates thymic TSHR gene expression and facilitates escape of TSHR-reactive T cells from central tolerance, triggering GD.

Role of promyelocytic leukemia zinc finger (PLZF) in cell proliferation and cyclin-dependent kinase inhibitor 1A (p21WAF/CDKN1A) gene repression

Promyelocytic leukemia zinc finger (PLZF) is a transcription repressor that was initially isolated as a fusion protein with retinoic acid receptor α. PLZF is aberrantly overexpressed in various human solid tumors, such as clear cell renal carcinoma, glioblastoma, and seminoma. PLZF causes cellular transformation of NIH3T3 cells and increases cell proliferation in several cell types. PLZF also increases tumor growth in the mouse xenograft tumor model. PLZF may stimulate cell proliferation by controlling expression of the genes of the p53 pathway (ARF, TP53, and CDKN1A). We found that PLZF can directly repress transcription of CDKN1A encoding p21, a negative regulator of cell cycle progression. PLZF binds to the proximal Sp1-binding GC-box 5/6 and the distal p53-responsive elements of the CDKN1A promoter to repress transcription. Interestingly, PLZF interacts with Sp1 or p53 and competes with Sp1 or p53. PLZF interacts with corepressors, such as mSin3A, NCoR, and SMRT, thereby deacetylates Ac-H3 and Ac-H4 histones at the CDKN1A promoter, which indicated the involvement of the corepressor·HDACs complex in transcription repression by PLZF. Also, PLZF represses transcription of TP53 and also decreases p53 protein stability by ubiquitination. PLZF may act as a potential proto-oncoprotein in various cell types.

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

The differentiation of early B-cell precursors in the bone marrow into the variety of mature and effector B-cell subsets of the periphery is a complex process that requires tight regulation at the transcriptional level. Different members of the broad complex, tramtrack, bric-à-brac and zinc finger (BTB-ZF) family of transcription factors have recently been shown to have key roles in many phases of B-cell development, including early B-cell development in the bone marrow, peripheral B-cell maturation and specialization into effector cells during an immune response. This review highlights the critical functions mediated by BTB-ZF transcription factors within the B-cell lineage and emphasizes how the deregulation of these transcription factors can lead to B-cell malignancies.

Paracrine mechanisms involved in the control of early stages of Mammalian spermatogenesis

Within the testis, Sertoli-cell is the primary target of pituitary FSH. Several growth factors have been described to be produced specifically by Sertoli cells and modulate male germ cell development through paracrine mechanisms. Some have been shown to act directly on spermatogonia such as GDNF, which acts on self-renewal of spermatogonial stem cells (SSCs) while inhibiting their differentiation; BMP4, which has both a proliferative and differentiative effect on these cells, and KIT ligand (KL), which stimulates the KIT tyrosine-kinase receptor expressed by differentiating spermatogonia (but not by SSCs). KL not only controls the proliferative cycles of KIT-positive spermatogonia, but it also stimulates the expression of genes that are specific of the early phases of meiosis, whereas the expression of typical spermatogonial markers is down-regulated. On the contrary, FGF9 acts as a meiotic inhibiting substance both in fetal gonocytes and in post-natal spermatogonia through the induction of the RNA-binding protein NANOS2. Vitamin A, which is metabolized to Retinoic Acid in Sertoli cells, controls both SSCs differentiation through KIT induction and NANOS2 inhibition, and meiotic entry of differentiating spermatogonia through STRA8 upregulation.

Hox5 interacts with Plzf to restrict Shh expression in the developing forelimb

To date, only the five most posterior groups of Hox genes, Hox9-Hox13, have demonstrated loss-of-function roles in limb patterning. Individual paralog groups control proximodistal patterning of the limb skeletal elements. Hox9 genes also initiate the onset of Hand2 expression in the posterior forelimb compartment, and collectively, the posterior HoxA/D genes maintain posterior Sonic Hedgehog (Shh) expression. Here we show that an anterior Hox paralog group, Hox5, is required for forelimb anterior patterning. Deletion of all three Hox5 genes (Hoxa5, Hoxb5, and Hoxc5) leads to anterior forelimb defects resulting from derepression of Shh expression. The phenotype requires the loss of all three Hox5 genes, demonstrating the high level of redundancy in this Hox paralogous group. Further analyses reveal that Hox5 interacts with promyelocytic leukemia zinc finger biochemically and genetically to restrict Shh expression. These findings, along with previous reports showing that point mutations in the Shh limb enhancer lead to similar anterior limb defects, highlight the importance of Shh repression for proper patterning of the vertebrate limb.

PLZF regulates fibroblast growth factor responsiveness and maintenance of neural progenitors

A transcription factor called Promyelocytic Leukemia Zinc Finger (PLZF) calibrates the balance between spinal cord progenitor maintenance and differentiation by enhancing their sensitivity to mitogens that are present in developing embryos.

Distinct classes of neurons and glial cells in the developing spinal cord arise at specific times and in specific quantities from spatially discrete neural progenitor domains. Thus, adjacent domains can exhibit marked differences in their proliferative potential and timing of differentiation. However, remarkably little is known about the mechanisms that account for this regional control. Here, we show that the transcription factor Promyelocytic Leukemia Zinc Finger (PLZF) plays a critical role shaping patterns of neuronal differentiation by gating the expression of Fibroblast Growth Factor (FGF) Receptor 3 and responsiveness of progenitors to FGFs. PLZF elevation increases FGFR3 expression and STAT3 pathway activity, suppresses neurogenesis, and biases progenitors towards glial cell production. In contrast, PLZF loss reduces FGFR3 levels, leading to premature neuronal differentiation. Together, these findings reveal a novel transcriptional strategy for spatially tuning the responsiveness of distinct neural progenitor groups to broadly distributed mitogenic signals in the embryonic environment.

The embryonic spinal cord is organized into an array of discrete neural progenitor domains along the dorsoventral axis. Most of these domains undergo two periods of differentiation, first producing specific classes of neurons and then generating distinct populations of glial cells at later times. In addition, each of these progenitors pools exhibit marked differences in their proliferative capacities and propensity to differentiate to produce the appropriate numbers and diversity of neurons and glia needed to form functional neural circuits. The mechanisms behind this regional control of neural progenitor behavior, however, remain unclear. In this study, we identify the transcription factor Promyelocytic Leukemia Zinc Finger (PLZF) as a critical regulator of this process in the chick spinal cord. We show that PLZF is initially expressed by all spinal cord progenitors and then becomes restricted to a central domain, where it helps to limit the rate of neuronal differentiation and to preserve the progenitor pool for subsequent glial production. We also demonstrate that PLZF acts by promoting the expression of Fibroblast Growth Factor (FGF) Receptor 3, thereby enhancing the proliferative response of neural progenitors to FGFs present in developing embryos. Together, these findings reveal a novel developmental strategy for spatially controlling neural progenitor behavior by tuning their responsiveness to broadly distributed growth-promoting signals in the embryonic environment.

Hox genes regulation in vertebrates

Hox genes encode transcription factors defining cellular identities along the major and secondary body axes. Their coordinated expression in both space and time is critical for embryonic patterning. Accordingly, Hox genes transcription is tightly controlled at multiple levels, and involves an intricate combination of local and long-range cis-regulatory elements. Recent studies revealed that in addition to transcription factors, dynamic patterns of histone marks and higher-order chromatin structure are important determinants of Hox gene regulation. Furthermore, the emerging picture suggests an involvement of various species of non-coding RNA in targeting activating and repressive complexes to Hox clusters. I review these recent developments and discuss their relevance to the control of Hox gene expression in vivo, as well as to our understanding of transcriptional regulatory mechanisms.

Canonical RTK-Ras-ERK signaling and related alternative pathways

Receptor Tyrosine Kinase (RTK)-Ras-Extracellular signal-regulated kinase (ERK) signaling pathways control many aspects of C. elegans development and behavior. Studies in C. elegans helped elucidate the basic framework of the RTK-Ras-ERK pathway and continue to provide insights into its complex regulation, its biological roles, how it elicits cell-type appropriate responses, and how it interacts with other signaling pathways to do so. C. elegans studies have also revealed biological contexts in which alternative RTK- or Ras-dependent pathways are used instead of the canonical pathway.

Plzf drives MLL-fusion-mediated leukemogenesis specifically in long-term hematopoietic stem cells

Oncogenic transformation requires unlimited self-renewal. Currently, it remains unclear whether a normal capacity for self-renewal is required for acquiring an aberrant self-renewal capacity. Our results in a new conditional transgenic mouse showed that a mixed lineage leukemia (MLL) fusion oncogene, MLL-ENL, at an endogenous-like expression level led to leukemic transformation selectively in a restricted subpopulation of hematopoietic stem cells (HSCs) through upregulation of promyelocytic leukemia zinc finger (Plzf). Interestingly, forced expression of Plzf itself immortalized HSCs and myeloid progenitors in vitro without upregulation of Hoxa9/Meis1, which are well-known targets of MLL fusion proteins, whereas its mutant lacking the BTB/POZ domain did not. In contrast, depletion of Plzf suppressed the MLL-fusion-induced leukemic transformation of HSCs in vitro and in vivo. Gene expression analyses of human clinical samples showed that a subtype of PLZF-high MLL-rearranged myeloid leukemia cells was closely associated with the gene expression signature of HSCs. These findings suggested that MLL fusion protein enhances the self-renewal potential of normal HSCs to develop leukemia, in part through a Plzf-driven self-renewal program.

The epigenetic regulator PLZF represses L1 retrotransposition in germ and progenitor cells

Germ cells and adult stem cells maintain tissue homeostasis through a finely tuned program of responses to both physiological and stress-related signals. PLZF (Promyelocytic Leukemia Zinc Finger protein), a member of the POK family of transcription factors, acts as an epigenetic regulator of stem cell maintenance in germ cells and haematopoietic stem cells. We identified L1 retrotransposons as the primary targets of PLZF. PLZF-mediated DNA methylation induces silencing of the full-length L1 gene and inhibits L1 retrotransposition. Furthermore, PLZF causes the formation of barrier-type boundaries by acting on inserted truncated L1 sequences in protein coding genes. Cell stress releases PLZF-mediated repression, resulting in L1 activation/retrotransposition and impaired spermatogenesis and myelopoiesis. These results reveal a novel mechanism of action by which, PLZF represses retrotransposons, safeguarding normal progenitor homeostasis.

Tzfp represses the androgen receptor in mouse testis

The testis zinc finger protein (Tzfp), also known as Repressor of GATA, belongs to the BTB/POZ zinc finger family of transcription factors and is thought to play a role in spermatogenesis due to its remarkably high expression in testis. Despite many attempts to find the in vivo role of the protein, the molecular function is still largely unknown. Here, we address this issue using a novel mouse model with a disrupted Tzfp gene. Homozygous Tzfp null mice are born at reduced frequency but appear viable and fertile. Sertoli cells in testes lacking Tzfp display an increase in Androgen Receptor (AR) signaling, and several genes in the testis, including Gata1, Aie1 and Fanc, show increased expression. Our results indicate that Tzfp function as a transcriptional regulator and that loss of the protein leads to alterations in AR signaling and reduced number of apoptotic cells in the testicular tubules.

Deciphering HIC1 control pathways to reveal new avenues in cancer therapeutics

INTRODUCTION

The tumor suppressor gene HIC1 (Hypermethylated in Cancer 1), which encodes a transcriptional repressor with multiple partners and multiple targets, is epigenetically silenced but not mutated in tumors. HIC1 has broad biological roles during normal development and is implicated in many canonical processes of cancer such as control of cell growth, cell survival upon genotoxic stress, cell migration, and motility.

AREAS COVERED

The HIC1 literature herein discussed includes its discovery as a candidate tumor suppressor gene hypermethylated or deleted in many human tumors, animal models establishing it as tumor suppressor gene, its role as a sequence-specific transcriptional repressor recruiting several chromatin regulatory complexes, its cognate target genes, and its functional roles in normal tissues. Finally, this review discusses how its loss of function contributes to the early steps in tumorigenesis.

EXPERT OPINION

Given HIC1's ability to direct repressive complexes to sequence-specific binding sites associated with its target genes, its loss results in specific changes in the transcriptional program of the cell. An understanding of this program through identification of HIC1's target genes and their involvement in feedback loops and cell process regulation will yield the ability to leverage this knowledge for therapeutic translation.

Cys2His2 zinc finger protein family: classification, functions, and major members

Cys2His2 (C2H2)-type zinc fingers are widespread DNA binding motifs in eukaryotic transcription factors. Zinc fingers are short protein motifs composed of two or three β-layers and one α-helix. Two cysteine and two histidine residues located in certain positions bind zinc to stabilize the structure. Four other amino acid residues localized in specific positions in the N-terminal region of the α-helix participate in DNA binding by interacting with hydrogen donors and acceptors exposed in the DNA major groove. The number of zinc fingers in a single protein can vary over a wide range, thus enabling variability of target DNA sequences. Besides DNA binding, zinc fingers can also provide protein-protein and RNA-protein interactions. For the most part, proteins containing the C2H2-type zinc fingers are trans regulators of gene expression that play an important role in cellular processes such as development, differentiation, and suppression of malignant cell transformation (oncosuppression).

UDP-GlcNAc 2-Epimerase/ManNAc Kinase (GNE): A Master Regulator of Sialic Acid Synthesis

UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase is the key enzyme of sialic acid biosynthesis in vertebrates. It catalyzes the first two steps of the cytosolic formation of CMP-N-acetylneuraminic acid from UDP-N-acetylglucosamine. In this review we give an overview of structure, biochemistry, and genetics of the bifunctional enzyme and its complex regulation. Furthermore, we will focus on diseases related to UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase.

Memories from the polycomb group proteins

The first genes composing the Polycomb group (PcG) were identified 50 years ago in Drosophila melanogaster as essential developmental functions that regulate the correct segmental expression of homeotic selector genes. In the past two decades, what was initially described as a large family of chromatin-associated proteins involved in the maintenance of transcriptional repression to maintain cellular memory of homeotic genes turned out to be a highly conserved and sophisticated network of epigenetic regulators that play key roles in multiple aspects of cell physiology and identity, including regulation of all developmental genes, cell differentiation, stem and somatic cell reprogramming and response to environmental stimuli. These myriad phenotypes further spread interest for the contribution that PcG proteins revealed in the pathogenesis and progression of cancer and other complex diseases. Recent novel insights have increasingly clarified the molecular regulatory mechanisms at the basis of PcG-mediated epigenetic silencing and opened new visions about PcG functions in cells. In this review, we focus on the multiple modes of action of the PcG complexes and describe their biological roles.

Functional antagonism between Sall4 and Plzf defines germline progenitors

Transcription factors required for formation of embryonic tissues often maintain their expression in adult stem cell populations, but whether their function remains equivalent is not clear. Here we demonstrate critical and distinct roles for Sall4 in development of embryonic germ cells and differentiation of postnatal spermatogonial progenitor cells (SPCs). In differentiating SPCs, Sall4 levels transiently increase and Sall4 physically interacts with Plzf, a transcription factor exclusively required for adult stem cell maintenance. Mechanistically, Sall4 sequesters Plzf to noncognate chromatin domains to induce expression of Kit, a target of Plzf-mediated repression required for differentiation. Plzf in turn antagonizes Sall4 function by displacing Sall4 from cognate chromatin to induce Sall1 expression. Taken together, these data suggest that transcription factors required for embryonic tissue development postnatally take on distinct roles through interaction with opposing factors, which hence define properties of the adult stem cell compartment.

The promyelocytic leukemia zinc finger protein: two decades of molecular oncology

The promyelocytic leukemia zinc finger (PLZF) protein, also known as Zbtb16 or Zfp145, was first identified in a patient with acute promyelocytic leukemia, where a reciprocal chromosomal translocation t(11;17)(q23;q21) resulted in a fusion with the RARA gene encoding retinoic acid receptor alpha. The wild-type Zbtb16 gene encodes a transcription factor that belongs to the POK (POZ and Krüppel) family of transcriptional repressors. In addition to nine Krüppel-type sequence-specific zinc fingers, which make it a member of the Krüppel-like zinc finger protein family, the PLZF protein contains an N-terminal BTB/POZ domain and RD2 domain. PLZF has been shown to be involved in major developmental and biological processes, such as spermatogenesis, hind limb formation, hematopoiesis, and immune regulation. PLZF is localized mainly in the nucleus where it exerts its transcriptional repression function, and many post-translational modifications affect this ability and also have an impact on its cytoplasmic/nuclear dissociation. PLZF achieves its transcriptional regulation by binding to many secondary molecules to form large multi-protein complexes that bind to the regulatory elements in the promoter region of the target genes. These complexes are also capable of physically interacting with its target proteins. Recently, PLZF has become implicated in carcinogenesis as a tumor suppressor gene, since it regulates the cell cycle and apoptosis in many cell types. This review will examine the major advances in our knowledge of PLZF biological activities that augment its value as a therapeutic target, particularly in cancer and immunological diseases.

Integration of the transcriptional networks regulating limb morphogenesis

The developing limb is one of the best described vertebrate systems for understanding how coordinated gene expression during embryogenesis leads to the structures present in the mature organism. This knowledge, derived from decades of research, is largely based upon gain- and loss-of-function experiments. These studies have provided limited information about how the key signaling pathways interact with each other and the downstream effectors of these pathways. We summarize our current understanding of known genetic interactions in the context of three temporally defined gene regulatory networks. These networks crystallize our current knowledge, depicting a dynamic process involving multiple feedback loops between the ectoderm and mesoderm. At the same time, they highlight the fact that many essential processes are still largely undescribed. Much of the dynamic transcriptional activity occurring during development is regulated by distal cis-regulatory elements. Modern genomic tools have provided new approaches for studying the function of cis-regulatory elements and we discuss the results of these studies in regard to understanding limb development. Ultimately, these genomic techniques will allow scientists to understand how multiple signaling pathways are integrated in space and time to drive gene expression and regulate the formation of the limb.