von Hippel-Lindau partner Jade-1 is a transcriptional co-activator associated with histone acetyltransferase activity

Multifunctional acyltransferase HBO1: a key regulatory factor for cellular functions

HBO1, also known as KAT7 or MYST2, is a crucial histone acetyltransferase with diverse cellular functions. It typically forms complexes with protein subunits or cofactors such as MEAF6, ING4, or ING5, and JADE1/2/3 or BRPF1/2/3, where the BRPF or JADE proteins serve as the scaffold targeting histone H3 or H4, respectively. The histone acetylation mediated by HBO1 plays significant roles in DNA replication and gene expression regulation. Additionally, HBO1 catalyzes the modification of proteins through acylation with propionyl, butyryl, crotonyl, benzoyl, and acetoacetyl groups. HBO1 undergoes ubiquitination and degradation by two types of ubiquitin complexes and can also act as an E3 ubiquitin ligase for the estrogen receptor α (ERα). Moreover, HBO1 participates in the expansion of medullary thymic epithelial cells (mTECs) and regulates the expression of peripheral tissue genes (PTGs) mediated by autoimmune regulator (AIRE), thus inducing immune tolerance. Furthermore, HBO1 influences the renewal of hematopoietic stem cells and the development of neural stem cells significantly. Importantly, the overexpression of HBO1 in various cancers suggests its carcinogenic role and potential as a therapeutic target. This review summarizes recent advancements in understanding HBO1's involvement in acylation modification, DNA replication, ubiquitination, immunity, and stem cell renewal.

MicroRNA-135b mainly functions as an oncogene during tumor progression

Late diagnosis is considered one of the main reasons of high mortality rate among cancer patients that results in therapeutic failure and tumor relapse. Therefore, it is needed to evaluate the molecular mechanisms associated with tumor progression to introduce efficient markers for the early tumor detection among cancer patients. The remarkable stability of microRNAs (miRNAs) in body fluids makes them potential candidates to use as the non-invasive tumor biomarkers in cancer screening programs. MiR-135b has key roles in prognosis and survival of cancer patients by either stimulating or inhibiting cell proliferation, invasion, and angiogenesis. Therefore, in the present review we assessed the molecular biology of miR-135b during tumor progression to introduce that as a novel tumor marker in cancer patients. It has been reported that miR-135b mainly acts as an oncogene by regulation of transcription factors, signaling pathways, drug response, cellular metabolism, and autophagy. This review paves the way to suggest miR-135b as a tumor marker and therapeutic target in cancer patients following the further clinical trials and animal studies.

Evaluating the Cellular Roles of the Lysine Acetyltransferase Tip60 in Cancer: A Multi-Action Molecular Target for Precision Oncology

Precision (individualized) medicine relies on the molecular profiling of tumors' dysregulated characteristics (genomic, epigenetic, transcriptomic) to identify the reliance on key pathways (including genome stability and epigenetic gene regulation) for viability or growth, and then utilises targeted therapeutics to disrupt these survival-dependent pathways. Non-mutational epigenetic changes alter cells' transcriptional profile and are a key feature found in many tumors. In contrast to genetic mutations, epigenetic changes are reversable, and restoring a normal epigenetic profile can inhibit tumor growth and progression. Lysine acetyltransferases (KATs or HATs) protect genome stability and integrity, and Tip60 is an essential acetyltransferase due to its roles as an epigenetic and transcriptional regulator, and as master regulator of the DNA double-strand break response. Tip60 is commonly downregulated and mislocalized in many cancers, and the roles that mislocalized Tip60 plays in cancer are not well understood. Here we categorize and discuss Tip60-regulated genes, evaluate Tip60-interacting proteins based on cellular localization, and explore the therapeutic potential of Tip60-targeting compounds as epigenetic inhibitors. Understanding the multiple roles Tip60 plays in tumorigenesis will improve our understanding of tumor progression and will inform therapeutic options, including informing potential combinatorial regimes with current chemotherapeutics, leading to improvements in patient outcomes.

JADE1 is dispensable for the brain development in mice

In mammalian brain development, WNT signaling balances proliferation and differentiation of neural progenitor cells, and is essential for the maintenance of regular brain development. JADE1 is a candidate transcription co-factor essential for DNA replication, cell division, and cell cycle regulation. In 293T cells, JADE1 is stabilized by von Hippel-Lindau protein pVHL, promotes the β-catenin ubiquitination and thus blunts canonical WNT signaling. Furthermore, JADE1 inhibits β-catenin-induced ectopic axis formation in Xenopus embryos. However, JADE1's role in mammalian brain development remains unknown. Here, we generated a new Jade1 knockout mouse line using CRISPR-Cas9 technology. We found that JADE1 null resulted in decreased survival rate, reduced body weight and brain weight in mice. However, histological analysis revealed a normal brain development. Furthermore, Jade1 null neural progenitor cells proliferated normally in vivo and in vitro. RNA-seq analysis further showed that JADE1 loss did not affect the cerebral cortex gene expression. Our findings indicate that JADE1 is dispensable for developing the cerebral cortex in mice.

Genetic Association and Differential RNA Expression of Histone (De)Acetylation-Related Genes in Pemphigus Foliaceus-A Possible Epigenetic Effect in the Autoimmune Response

Pemphigus foliaceus (PF) is an autoimmune skin blistering disease characterized by antidesmoglein-1 IgG production, with an endemic form (EPF) in Brazil. Genetic and epigenetic factors have been associated with EPF, but its etiology is still not fully understood. To evaluate the genetic association of histone (de)acetylation-related genes with EPF susceptibility, we evaluated 785 polymorphisms from 144 genes, for 227 EPF patients and 194 controls. Carriers of HDAC4_rs4852054*A were more susceptible (OR = 1.79, p = 0.0038), whereas those with GSE1_rs13339618*A (OR = 0.57, p = 0.0011) and homozygotes for PHF21A_rs4756055*A (OR = 0.39, p = 0.0006) were less susceptible to EPF. These variants were not associated with sporadic PF (SPF) in German samples of 75 SPF patients and 150 controls, possibly reflecting differences in SPF and EPF pathophysiology. We further evaluated the expression of histone (de)acetylation-related genes in CD4+ T lymphocytes, using RNAseq. In these cells, we found a higher expression of KAT2B, PHF20, and ZEB2 and lower expression of KAT14 and JAD1 in patients with active EPF without treatment compared to controls from endemic regions. The encoded proteins cause epigenetic modifications related to immune cell differentiation and cell death, possibly affecting the immune response in patients with PF.

An Analysis of JADE2 in Non-Small Cell Lung Cancer (NSCLC)

The JADE family comprises three members encoded by individual genes and roles for these proteins have been identified in chromatin remodeling, cell cycle progression, cell regeneration and the DNA damage response. JADE family members, and in particular JADE2 have not been studied in any great detail in cancer. Using a series of standard biological and bioinformatics approaches we investigated JADE2 expression in surgically resected non-small cell lung cancer (NSCLC) for both mRNA and protein to examine for correlations between JADE2 expression and overall survival. Additional correlations were identified using bioinformatic analyses on multiple online datasets. Our analysis demonstrates that JADE2 expression is significantly altered in NSCLC. High expression of JADE2 is associated with a better 5-year overall survival. Links between JADE2 mRNA expression and a number of mutated genes were identified, and associations between JADE2 expression and tumor mutational burden and immune cell infiltration were explored. Potential new drugs that can target JADE2 were identified. The results of this biomarker-driven study suggest that JADE2 may have potential clinical utility in the diagnosis, prognosis and stratification of patients into various therapeutically targetable options.

Excessive All-Trans Retinoic Acid Inhibits Cell Proliferation Through Upregulated MicroRNA-4680-3p in Cultured Human Palate Cells

Cleft palate is the second most common congenital birth defect, and both environmental and genetic factors are involved in the etiology of the disease. However, it remains largely unknown how environmental factors affect palate development. Our previous studies show that several microRNAs (miRs) suppress the expression of genes involved in cleft palate. Here we show that miR-4680-3p plays a crucial role in cleft palate pathogenesis. We found that all-trans retinoic acid (atRA) specifically induces miR-4680-3p in cultured human embryonic palatal mesenchymal (HEPM) cells. Overexpression of miR-4680-3p inhibited cell proliferation in a dose-dependent manner through the suppression of expression of ERBB2 and JADE1, which are known cleft palate-related genes. Importantly, a miR-4680-3p-specific inhibitor normalized cell proliferation and altered expression of ERBB2 and JADE1 in cells treated with atRA. Taken together, our results suggest that upregulation of miR-4680-3p induced by atRA may cause cleft palate through suppression of ERBB2 and JADE1. Thus, miRs may be potential targets for the prevention and diagnosis of cleft palate.

Silencing of microRNA-135b inhibits invasion, migration, and stemness of CD24+CD44+ pancreatic cancer stem cells through JADE-1-dependent AKT/mTOR pathway

Background

Recent studies have emphasized determining the ability of microRNAs (miRNAs) as crucial regulators in the occurrence and development of pancreatic cancer (PC), which continues to be one of the deadliest malignancies with few effective therapies. The study aimed to investigate the functional role of miR-135b and its associated mechanism to unravel the biological characteristics of tumor growth in pancreatic cancer stem cells (PCSCs).

Methods

Microarray analyses were initially performed to identify the PC-related miRNAs and genes. The expression of miR-135b and PCSC markers in PC tissues and cells was determined by RT-qPCR and western blot analysis, respectively. The potential gene (JADE-1) that could bind to miR-135b was confirmed by the dual-luciferase reporter assay. To investigate the tumorigenicity, migration, invasion, and stemness of PC cells, several gain-of-function and loss-of-function genetic experiments were conducted. Finally, tumor formation in nude mice was conducted to confirm the results in vivo.

Results

miR-135b was highly-expressed in PC tissues and PCSCs, which was identified to specifically target JADE-1. The overexpression of miR-135b promoted proliferation, migration, and invasion of PCSC, inhibited cell apoptosis and increased the expression of stemness-related factors (Sox-2, Oct-4, Nanog, Aldh1, and Slug). Moreover, miR-135b could promote the expression of phosphorylated AKT and phosphorylated mTOR in the AKT/mTOR pathway. Additionally, miR-135b overexpression accelerated tumor growth in nude mice.

Conclusions

Taken together, the silencing of miR-135b promotes the JADE-1 expression, which inactivates the AKT/mTOR pathway and ultimately results in inhibition of self-renewal and tumor growth of PCSCs. Hence, this study contributes to understanding the role of miR-135 in PCSCs and its underlying molecular mechanisms to aid in the development of effective PC therapeutics.

Structural basis for renal cancer by the dynamics of pVHL-dependent JADE1 stabilization and β-catenin regulation

Renal cancer is the major cause of mortality due to abnormal functioning of von Hippel-Lindau (pVHL) and Jade Family PHD Finger 1 (JADE1) complex. E3 ubiquitin ligase JADE1 is stabilized by pVHL interaction through its plant homeodomains (PHDs). JADE1 acts as a renal tumor suppressor that promotes the ubiquitination and degradation of β-catenin by inhibiting canonical WNT signalling. Current study focuses on the structural characterization of reported missense mutations in pVHL through in silico approaches. The predicted 3-dimensional structures of pVHL^WT, pVHL^Y98H, pVHL^Y112H, pVHL^L118P and pVHL^R167W were subjected to binding analysis against JADE1 through molecular docking and simulation assays. In all cases, JADE1 binding was observed at the β-domain, except pVHL^L118P that exhibited binding with JADE1 through its α-domain. Our results signify that JADE1 stabilization is induced by pVHL α-domain, while β-domain is required for JADE1 binding. pVHL binding was mediated through β1 and β2-strands against the concave surface of the JADE1-PHD domain. The pVHL-JADE1 complex was evaluated to scrutinize the β-catenin-binding interface, which suggested the contribution of both α and β-domains of pVHL in β-catenin binding. The eleven-residue (Tyr30-Thr40) β-catenin segment exhibited association in a bipartite manner with pVHL-JADE1 complex. The presented model depicts a pVHL-JADE1 interface for the cooperative regulation of β-catenin binding. We propose that reduced JADE1 stabilization in case of pVHL^L118P and pVHL^R167W may correlate with the increased activity of β-catenin that may lead to renal cancer through β-catenin de-repression. Overall, β-catenin targeting mechanism coupled with the structural knowledge of JADE1-pVHL complex will provide better understanding of renal cancer pathogenesis.

Comprehensive profiling of transcriptional networks specific for lactogenic differentiation of HC11 mammary epithelial stem-like cells

The development of mammary gland as a lactogenic tissue is a highly coordinated multistep process. The epithelial cells of lactiferous tubules undergo profound changes during the developmental window of puberty, pregnancy, and lactation. Several hormones including estrogen, progesterone, glucocorticoids and prolactin act in concert, and orchestrate the development of mammary gland. Understanding the gene regulatory networks that coordinate proliferation and differentiation of HC11 Mammary Epithelial stem-like Cells (MEC) under the influence of lactogenic hormones is critical for elucidating the mechanism of lactogenesis in detail. In this study, we analyzed transcriptome profiles of undifferentiated MEC (normal) and compared them with Murine Embryonic Stem Cells (ESC) using next-generation mRNA sequencing. Further, we analyzed the transcriptome output during lactogenic differentiation of MEC following treatment with glucocorticoids (primed state) and both glucocorticoids and prolactin together (prolactin state). We established stage-specific gene regulatory networks in ESC and MEC (normal, priming and prolactin states). We validated the top up-and downregulated genes in each stage of differentiation of MEC by RT-PCR and found that they are comparable with that of RNA-seq data. HC11 MEC display decreased expression of Pou5f1 and Sox2, which is crucial for the differentiation of MEC, which otherwise ensure pluripotency to ESC. Cited4 is induced during priming and is involved in milk secretion. MEC upon exposure to both glucocorticoids and prolactin undergo terminal differentiation, which is associated with the expression of several genes, including Xbp1 and Cbp that are required for cell growth and differentiation. Our study also identified differential expression of transcription factors and epigenetic regulators in each stage of lactogenic differentiation. We also analyzed the transcriptome data for the pathways that are selectively activated during lactogenic differentiation. Further, we found that selective expression of chromatin modulators (Dnmt3l, Chd9) in response to glucocorticoids suggests a highly coordinated stage-specific lactogenic differentiation of MEC.

The von Hippel–Lindau Tumor Suppressor Protein

The von Hippel–Lindau (VHL) gene is a two-hit tumor suppressor gene and is linked to the development of the most common form of kidney cancer, clear cell renal carcinoma; blood vessel tumors of the retina, cerebellum, and spinal cord called hemangioblastomas; and tumors of the sympathoadrenal nervous system called paragangliomas. The VHL gene product, pVHL, is the substrate recognition subunit of a cullin-dependent ubiquitin ligase that targets the α subunits of hypoxia-inducible factor (HIF) for destruction when oxygen is plentiful. Mounting evidence implicates HIF2 in the pathogenesis of pVHL-defective tumors and has provided a conceptual foundation for the development of drugs to treat them that inhibit HIF2-responsive gene products such as VEGF and, more recently, HIF2 itself. pVHL has additional, noncanonical functions that are cancer relevant, including roles related to the primary cilium, chromosome stability, extracellular matrix formation, and survival signaling.

Renal Carcinogenesis, Tumor Heterogeneity, and Reactive Oxygen Species: Tactics Evolved

SIGNIFICANCE

The number of kidney cancers is growing 3-5% each year due to unknown etiologies. Intra- and inter-tumor mediators increase oxidative stress and drive tumor heterogeneity. Recent Advances: Technology advancement in state-of-the-art instrumentation and methodologies allows researchers to detect and characterize global landscaping modifications in genes, proteins, and pathophysiology patterns at the single-cell level.

CRITICAL ISSUES

We postulate that the sources of reactive oxygen species (ROS) and their activation within subcellular compartments will change over a timeline of tumor evolvement and contribute to tumor heterogeneity. Therefore, the complexity of intracellular changes within a tumor and ROS-induced tumor heterogeneity coupled to the advancement of detecting these events globally are limited at the level of data collection, organization, and interpretation using software algorithms and bioinformatics.

FUTURE DIRECTIONS

Integrative and collaborative research, combining the power of numbers with careful experimental design, protocol development, and data interpretation, will translate cancer biology and therapeutics to a heightened level or leave the abundant raw data as stagnant and underutilized. Antioxid. Redox Signal. 25, 685-701.

Correlation analysis of VHL and Jade-1 gene expression in human renal cell carcinoma

Objective

The aim of this study was to investigate the correlation of von Hippel-Lindau tumor suppressor (VHL) mRNA expression and jade family PHD finger 1 (Jade-1) gene expression in patients with renal cell carcinoma (RCC). Another aim of this study was to analyze the relationship of these two genes with clinicalpathological features of the RCC patients.

Methods

A total of 75 RCC patients who received surgically therapy in our hospital were included. All patients had complete pathological data. The expression of VHL/Jade-1 was determined by real-time polymerase chain reaction (RT-PCR).

Results

VHL and Jade-1 were both obviously downregulated in RCC tissues than that of the matched normal tissues, and both negatively correlated with tumor size as well as tumor grade. And we found a fine association of VHL gene expression with Jade-1.

Conclusion

VHL/Jade-1 exhibited significantly decreased expression in RCC tissues and was closely related to the clinical prognosis of patients. The finding of VHL expression positively correlated with Jade-1 expression shed light and provided crucial evidence on the connection of VHL protein with Wnt/b-catenin pathway.

Structure, function and regulation of jade family PHD finger 1 (JADE1)

The family of JADE proteins includes three paralogues encoded by individual genes and designated PHF17 (JADE1), PHF16 (JADE2), and PHF15 (JADE3). All three JADE proteins bear in tandem two Plant Homeo-domains (PHD) which are zinc finger domains. This review focuses on one member of the JADE family, JADE1. Studies addressing the biochemical, cellular and biological role of JADE1 are discussed. Recent discoveries of JADE1 function in the regulation of the epithelial cell cycle with potential relevance to disease are presented. Unresolved questions and future directions are formulated.

Jade-1S phosphorylation induced by CK1α contributes to cell cycle progression

The PHD zinc finger protein Jade-1S is a component of the HBO1 histone acetyltransferase complex and binds chromatin in a cell cycle-dependent manner. Jade-1S also acts as an E3 ubiquitin ligase for the canonical Wnt effector protein β-catenin and is influenced by CK1α-mediated phosphorylation. To further elucidate the functional impact of this phosphorylation, we used a stable, low-level expression system to express either wild-type or mutant Jade-1S lacking the N-terminal CK1α phosphorylation motif. Interactome analyses revealed that the Jade-1S mutant unable to be phosphorylated by CK1α has an increased binding affinity to proteins involved in chromatin remodelling, histone deacetylation, transcriptional repression, and ribosome biogenesis. Interestingly, cells expressing the mutant displayed an elongated cell shape and a delay in cell cycle progression. Finally, phosphoproteomic analyses allowed identification of a Jade-1S site phosphorylated in the presence of CK1α but closely resembling a PLK1 phosphorylation motif. Our data suggest that Jade-1S phosphorylation at an N-terminal CK1α motif creates a PLK1 phospho-binding domain. We propose CK1α phosphorylation of Jade 1S to serve as a molecular switch, turning off chromatin remodelling functions of Jade-1S and allowing timely cell cycle progression. As Jade-1S protein expression in the kidney is altered upon renal injury, this could contribute to understanding mechanisms underlying epithelial injury repair.

UV Damage-Induced Phosphorylation of HBO1 Triggers CRL4DDB2-Mediated Degradation To Regulate Cell Proliferation

Histone acetyltransferase binding to ORC-1 (HBO1) is a critically important histone acetyltransferase for forming the prereplicative complex (pre-RC) at the replication origin. Pre-RC formation is completed by loading of the MCM2-7 heterohexameric complex, which functions as a helicase in DNA replication. HBO1 recruited to the replication origin by CDT1 acetylates histone H4 to relax the chromatin conformation and facilitates loading of the MCM complex onto replication origins. However, the acetylation status and mechanism of regulation of histone H3 at replication origins remain elusive. HBO1 positively regulates cell proliferation under normal cell growth conditions. Whether HBO1 regulates proliferation in response to DNA damage is poorly understood. In this study, we demonstrated that HBO1 was degraded after DNA damage to suppress cell proliferation. Ser50 and Ser53 of HBO1 were phosphorylated in an ATM/ATR DNA damage sensor-dependent manner after UV treatment. ATM/ATR-dependently phosphorylated HBO1 preferentially interacted with DDB2 and was ubiquitylated by CRL4(DDB2). Replacement of endogenous HBO1 in Ser50/53Ala mutants maintained acetylation of histone H3K14 and impaired cell cycle regulation in response to UV irradiation. Our findings demonstrate that HBO1 is one of the targets in the DNA damage checkpoint. These results show that ubiquitin-dependent control of the HBO1 protein contributes to cell survival during UV irradiation.

Familial syndromes associated with neuroendocrine tumours

Neuroendocrine tumours may be associated with familial syndromes. At least eight inherited syndromes predisposing to endocrine neoplasia have been identified. Two of these are considered to be major factors predisposing to benign and malignant endocrine tumours, designated multiple endocrine neoplasia type 1 and type 2 (MEN1 and MEN2). Five other autosomal dominant diseases show more heterogeneous clinical patterns, such as the Carney complex, hyperparathyroidism-jaw tumour syndrome, Von Hippel-Lindau syndrome (VHL), neurofibromatosis type 1 (NF1) and tuberous sclerosis. The molecular and cellular interactions underlying the development of most endocrine cells and related organs represent one of the more complex pathways not yet to be deciphered. Almost all endocrine cells are derived from the endoderm and neuroectoderm. It is suggested that within the first few weeks of human development there are complex interactions between, firstly, the major genes involved in the initiation of progenitor-cell differentiation, secondly, factors secreted by the surrounding mesenchyme, and thirdly, a series of genes controlling cell differentiation, proliferation and migration. Together these represent a formula for the harmonious development of endocrine glands and tissue.

The novel function of JADE1S in cytokinesis of epithelial cells

JADE1 belongs to a small family of PHD zinc finger proteins that interacts with histone acetyl transferase (HAT) HBO1 and is associated with chromatin. We recently reported JADE1 chromatin shuttling and phosphorylation during G2/M to G1 transition, which was sensitive to Aurora A inhibition. In the current study we examined mechanisms of the cell cycle regulation by the small isoform of JADE1 protein, JADE1S, and report data showing that JADE1S has a novel function in the regulation of cytokinesis. Using FACS assays, we show that, JADE1S depletion facilitated rates of G1-cells accumulation in synchronously dividing HeLa cell cultures. Depletion of JADE1S protein in asynchronously dividing cells decreased the proportion of cytokinetic cells, and increased the proportion of multi-nuclear cells, indicative of premature and failed cytokinesis. In contrast, moderate overexpression of JADE1S increased the number of cytokinetic cells in time- and dose- dependent manner, indicating cytokinetic delay. Pharmacological inhibition of Aurora B kinase resulted in the release of JADE1S-mediated cytokinetic delay and allowed progression of abscission in cells over-expressing JADE1S. Finally, we show that JADE1S protein localized to centrosomes in interphase and mitotic cells, while during cytokinesis JADE1S localized to the midbody. Neither JADE1L nor partner of JADE1, HAT HBO1 was localized to the centrosomes or midbodies. Our study identifies the novel role for JADE1S in regulation of cytokinesis and suggests function in Aurora B kinase-mediated cytokinesis checkpoint.

Antitumor effect and biological pathways of a recombinant adeno-associated virus as a human renal cell carcinoma suppressor

The aims of this work are to study the antitumor effect of the adeno-associated virus on the xenografted tumors of chick embryo chorioallantoic membrane and predict potential genes and biological pathways which are associated with renal cell carcinoma. The adeno-associated virus NT4-TAT-6 × His-VHLbeta was constructed and identified. Then, chick embryos with xenografted tumor were divided into three groups and respectively inoculated with rAAV/NT4-TAT-6 × His-VHLbeta (group A), empty virus (group B), and phosphate-buffered saline (group C, the control subject). Antitumor effect in each group was investigated by means of immunofluorescence observation. Genes interacted with von Hippel–Lindau were screened by Search Tool for the Retrieval of Interacting Genes/Proteins database, while pathway analysis were performed based on Kyoto Encyclopedia of Genes and Genomes. The growth of xenografted tumors inoculated with recombinant adeno-associated virus was slower than the control subjects. The tumor volumes of group A showed significant difference compared with group B and group C (P < 0.05). Growth of xenografted tumors which administered with the recombinant adeno-associated virus was inhibited. Among the protein–protein interaction network, TCEB2, HIF1A, TCEB1, CUL2, RBX1, and PHF17 were hub genes which might be involved in the development of renal cell carcinoma. The most significant signaling pathway was renal cell carcinoma. In this paper, we constructed and identified the recombinant adeno-associated virus NT4-TAT-6 × His-VHLbeta and studied the antitumor effect of the adeno-associated virus on xenografted tumors of chicken embryo chorioallantoic membrane. In addition, genes in the protein–protein interaction network which are associated with renal cell carcinoma were revealed and the biological pathway of renal cell carcinoma was identified. Our results provide a gene-therapeutic agent for the treatment of human renal cell carcinoma.

Destabilizing LSD1 by Jade-2 promotes neurogenesis: an antibraking system in neural development

Histone H3K4 demethylase LSD1 plays an important role in stem cell biology, especially in the maintenance of the silencing of differentiation genes. However, how the function of LSD1 is regulated and the differentiation genes are derepressed are not understood. Here, we report that elimination of LSD1 promotes embryonic stem cell (ESC) differentiation toward neural lineage. We showed that the destabilization of LSD1 occurs posttranscriptionally via the ubiquitin-proteasome pathway by an E3 ubiquitin ligase, Jade-2. We demonstrated that Jade-2 is a major LSD1 negative regulator during neurogenesis in vitro and in vivo in both mouse developing cerebral cortices and zebra fish embryos. Apparently, Jade-2-mediated degradation of LSD1 acts as an antibraking system and serves as a quick adaptive mechanism for re-establishing epigenetic landscape without more laborious transcriptional regulations. As a potential anticancer strategy, Jade-2-mediated LSD1 degradation could potentially be used in neuroblastoma cells to induce differentiation toward postmitotic neurons.

Cell cycle-dependent chromatin shuttling of HBO1-JADE1 histone acetyl transferase (HAT) complex

HAT HBO1 interacts with 2 isoforms of JADE1: JADE1S and JADE1L. JADE1 promotes acetylation of nucleosomal histones by HBO1. HBO1–JADE1 complex facilitates cell proliferation by unclear mechanisms. Here we report intracellular chromatin shuttling of HBO1–JADE1 complex during mitosis coupled to phosphorylation of JADE1. In interphase of dividing cells JADE1S was localized to the nucleus and associated with chromatin. As cells approached mitosis, specifically prophase, JADE1S dissociated from chromatin and associated with cytoplasm. JADE1S chromatin re-association began in telophase and paralleled nuclear envelope membrane reassembly. By early G₁, JADE1S was re-associated with chromatin and localized to the nucleus. Importantly, cytoplasmic but not chromatin-associated JADE1 protein was phosphorylated. Mass-Spectrometric analysis of JADE1S protein isolated from G₂/M-arrested cells identified 6 phosphorylated amino acid residues: S89, T92, S102, S121, S392, and T468, including 3 novel sites. Temporally, JADE1S phosphorylation and dephosphorylation during mitosis correlated with JADE1S chromatin dissociation and recruitment. JADE1S chromatin recruitment was accompanied by the global histone H4 acetylation. Pharmacological inhibitor of Aurora A kinase prevented JADE1S protein band shift and chromatin dissociation, suggesting regulatory function for phosphorylation. In vivo experiments supported our in vitro results. In mouse kidneys, JADE1S transiently accumulated in the cytoplasm of tubular epithelial cells during kidney regeneration. The transient increase in the number of cells with cytoplasmic JADE1S directly correlated with activation of tubular cell proliferation and inversely correlated with the number of cells with nuclear JADE1S staining, supporting biological role of HBO1–JADE1 shuttling during organ regeneration.

Mammalian epigenetic mechanisms

The mammalian genome is packaged into chromatin that is further compacted into three-dimensional structures consisting of distinct functional domains. The higher order structure of chromatin is in part dictated by enzymatic DNA methylation and histone modifications to establish epigenetic layers controlling gene expression and cellular functions, without altering the underlying DNA sequences. Apart from DNA and histone modifications, non-coding RNAs can also regulate the dynamics of the mammalian gene expression and various physiological functions including cell division, differentiation, and apoptosis. Aberrant epigenetic signatures are associated with abnormal developmental processes and diseases such as cancer. In this review, we will discuss the different layers of epigenetic regulation, including writer enzymes for DNA methylation, histone modifications, non-coding RNA, and chromatin conformation. We will highlight the combinatorial role of these structural and chemical modifications along with their partners in various cellular processes in mammalian cells. We will also address the cis and trans interacting "reader" proteins that recognize these modifications and "eraser" enzymes that remove these marks. Furthermore, an attempt will be made to discuss the interplay between various epigenetic writers, readers, and erasures in the establishment of mammalian epigenetic mechanisms.

Regulation of Wnt/β-catenin signaling by posttranslational modifications

The canonical Wnt signaling pathway (or Wnt/β-catenin pathway) plays a pivotal role in embryonic development and adult homeostasis; deregulation of the Wnt pathway contributes to the initiation and progression of human diseases including cancer. Despite its importance in human biology and disease, how regulation of the Wnt/β-catenin pathway is achieved remains largely undefined. Increasing evidence suggests that post-translational modifications (PTMs) of Wnt pathway components are essential for the activation of the Wnt/β-catenin pathway. PTMs create a highly dynamic relay system that responds to Wnt stimulation without requiring de novo protein synthesis and offer a platform for non-Wnt pathway components to be involved in the regulation of Wnt signaling, hence providing alternative opportunities for targeting the Wnt pathway. This review highlights the current status of PTM-mediated regulation of the Wnt/β-catenin pathway with a focus on factors involved in Wnt-mediated stabilization of β-catenin.

Regulation of the transcriptional activation of the androgen receptor by the UXT-binding protein VHL

Loss and/or inactivation of the VHL (von Hippel-Lindau) tumour suppressor causes various tumours. Using a yeast two-hybrid system, we have identified the AR (androgen receptor) co-activator UXT (ubiquitously expressed transcript), as a VHL-interacting protein. GST pull-down and co-immunoprecipitation assays show that UXT interacts with VHL. In addition, UXT recruits VHL to the nucleus. VHL associates with the DBD (DNA-binding domain) and hinge domains of the AR and induces AR ubiquitination. Moreover, VHL interaction with the AR activates AR transactivation upon DHT (dihydrotestosterone) treatment. VHL knockdown inhibits AR ubiquitination and decreases transcriptional activation of the AR. Our data suggest that the VHL-UXT interaction and VHL-induced ubiquitination of AR regulate transcriptional activation of the AR.

Depletion of PHF14, a novel histone-binding protein gene, causes neonatal lethality in mice due to respiratory failure

The plant homeodomain (PHD) finger is identified in many chromatin-binding proteins, and functions as a 'reader' that recognizes specific epigenetic marks on histone tails, bridging transcription factors and their associated complexes to chromatin, and regulating gene expression. PHD finger-containing proteins perform many biological functions and are involved in many human diseases including cancer. PHF14 is predicted to code for a protein with multiple PHD fingers. However, its function is unidentified. The aim of this study is to characterize PHF14 and investigate its biological significance by employing multiple approaches including mouse gene-targeting knockout, and molecular cloning and characterization. Three transcripts of PHF14 in human cell lines were identified by reverse transcriptase polymerase chain reaction. Two isoforms of PHF14 (PHF14α and PHF14β) were cloned in this study. It was found that PHF14 was ubiquitously expressed in mouse tissues and human cell lines. PHF14α, the major isoform of PHF14, was localized in the nucleus and also bound to chromatin during cell division. Interestingly, co-immunoprecipitation results suggested that PHF14α bound to histones via its PHD fingers. Strikingly, gene-targeting knockout of PHF14 in mice resulted in a neonatal lethality due to respiratory failure. Pathological analysis revealed severe disorders of tissue and cell structures in multiple organs, particularly in the lungs. These results indicated that PHF14 might be an epigenetic regulator and play an important role in the development of multiple organs in mouse.

Candidate tumor suppressor and pVHL partner Jade-1 binds and inhibits AKT in renal cell carcinoma

The von Hippel-Lindau (VHL) tumor suppressor pVHL is lost in the majority of clear-cell renal cell carcinomas (RCC). Activation of the PI3K/AKT/mTOR pathway is also common in RCC, with PTEN loss occurring in approximately 30% of the cases, but other mechanisms responsible for activating AKT at a wider level in this setting are undefined. Plant homeodomain protein Jade-1 (PHF17) is a candidate renal tumor suppressor stabilized by pVHL. Here, using kinase arrays, we identified phospho-AKT1 as an important target of Jade-1. Overexpressing or silencing Jade-1 in RCC cells increased or decreased levels of endogenous phospho-AKT/AKT1. Furthermore, reintroducing pVHL into RCC cells increased endogenous Jade-1 and suppressed endogenous levels of phospho-AKT, which colocalized with and bound to Jade-1. The N-terminus of Jade-1 bound both the catalytic domain and the C-terminal regulatory tail of AKT, suggesting a mechanism through which Jade-1 inhibited AKT kinase activity. Intriguingly, RCC precursor cells where Jade-1 was silenced exhibited an increased capacity for AKT-dependent anchorage-independent growth, in support of a tumor suppressor function for Jade-1 in RCC. In support of this concept, an in silico expression analysis suggested that reduced Jade-1 expression is a poor prognostic factor in clear-cell RCC that is associated with activation of an AKT1 target gene signature. Taken together, our results identify 2 mechanisms for Jade-1 fine control of AKT/AKT1 in RCC, through loss of pVHL, which decreases Jade-1 protein, or through attenuation in Jade-1 expression. These findings help explain the pathologic cooperativity in clear-cell RCC between PTEN inactivation and pVHL loss, which leads to decreased Jade-1 levels that superactivate AKT. In addition, they prompt further investigation of Jade-1 as a candidate biomarker and tumor suppressor in clear-cell RCC.

Histone acetyl transferase (HAT) HBO1 and JADE1 in epithelial cell regeneration

HBO1 acetylates lysine residues of histones and is involved in DNA replication and gene transcription. Two isoforms of JADE1, JADE1S and JADE1L, bind HBO1 and promote acetylation of histones in chromatin context. We characterized the role of JADE1-HBO1 complexes in vitro and in vivo during epithelial cell replication. Down-regulation of JADE1 by siRNA diminished the rate of DNA synthesis in cultured cells, decreased endogenous HBO1 protein expression, and prevented chromatin recruitment of replication factor Mcm7, demonstrating that JADE1 is required for cell proliferation. We used a murine model of acute kidney injury to examine expression of HBO1-JADE1S/L in injured and regenerating epithelial tissue. In control kidneys, JADE1S, JADE1L, and HBO1 were expressed in nuclei of proximal and distal tubular epithelial cells. Ischemia and reperfusion injury resulted in an initial decrease in JADE1S, JADE1L, and HBO1 protein levels, which returned to baseline during renal recovery. HBO1 and JADE1S recovered as cell proliferation reached its maximum, whereas JADE1L recovered after bulk proliferation had ceased. The temporal expression of JADE1S correlated with the acetylation of histone H4 on lysines 5 and 12, but not with acetylation of histone H3 on lysine 14, demonstrating that the JADE1S-HBO1 complex specifically marks H4 during epithelial cell proliferation. These data implicate JADE1-HBO1 complex in acute kidney injury and suggest distinct roles for JADE1 isoforms during epithelial cell recovery.

Polycystin-1 regulates the stability and ubiquitination of transcription factor Jade-1

Autosomal-dominant polycystic kidney disease (ADPKD) and von Hippel-Lindau (VHL) disease lead to large kidney cysts that share pathogenetic features. The polycystin-1 (PC1) and pVHL proteins may therefore participate in the same key signaling pathways. Jade-1 is a pro-apoptotic and growth suppressive ubiquitin ligase for beta-catenin and transcriptional coactivator associated with histone acetyltransferase activity that is stabilized by pVHL in a manner that correlates with risk of VHL renal disease. Thus, a relationship between Jade-1 and PC1 was sought. Full-length PC1 bound, stabilized and colocalized with Jade-1 and inhibited Jade-1 ubiquitination. In contrast, the cytoplasmic tail or the naturally occurring C-terminal fragment of PC1 (PC1-CTF) promoted Jade-1 ubiquitination and degradation, suggesting a dominant-negative mechanism. ADPKD-associated PC1 mutants failed to regulate Jade-1, indicating a potential disease link. Jade-1 ubiquitination was mediated by Siah-1, an E3 ligase that binds PC1. By controlling Jade-1 abundance, PC1 and the PC1-CTF differentially regulate Jade-1-mediated transcriptional activity. A key target of PC1, the cyclin-dependent kinase inhibitor p21, is also up-regulated by Jade-1. Through Jade-1, PC1 and PC1 cleaved forms may exert fine control of beta-catenin and canonical Wnt signaling, a critical pathway in cystic renal disease. Thus, Jade-1 is a transcription factor and ubiquitin ligase whose activity is regulated by PC1 in a manner that is physiologic and may correlate with disease. Jade-1 may be an important therapeutic target in renal cystogenesis.

Conserved molecular interactions within the HBO1 acetyltransferase complexes regulate cell proliferation

Acetyltransferase complexes of the MYST family with distinct substrate specificities and functions maintain a conserved association with different ING tumor suppressor proteins. ING complexes containing the HBO1 acetylase are a major source of histone H3 and H4 acetylation in vivo and play critical roles in gene regulation and DNA replication. Here, our molecular dissection of HBO1/ING complexes unravels the protein domains required for their assembly and function. Multiple PHD finger domains present in different subunits bind the histone H3 N-terminal tail with a distinct specificity toward lysine 4 methylation status. We show that natively regulated association of the ING4/5 PHD domain with HBO1-JADE determines the growth inhibitory function of the complex, linked to its tumor suppressor activity. Functional genomic analyses indicate that the p53 pathway is a main target of the complex, at least in part through direct transcription regulation at the initiation site of p21/CDKN1A. These results demonstrate the importance of ING association with MYST acetyltransferases in controlling cell proliferation, a regulated link that accounts for the reported tumor suppressor activities of these complexes.

Beta-catenin gets jaded and von Hippel-Lindau is to blame

Numerous studies have pointed to interactions between the tumor suppressor von Hippel-Lindau (VHL) and the oncogenic Wnt-beta-catenin signaling cascade; however, the mechanism of this crosstalk has remained elusive. Among other roles, VHL can promote the stabilization of Jade-1. Now, recent findings provide compelling evidence that Jade-1 ubiquitylates beta-catenin, leading to its degradation. Thus, the loss of VHL, as seen in clear cell renal cell carcinoma, could lead to tumor formation through beta-catenin de-repression.

Comparative transcriptional analysis of embryoid body versus two-dimensional differentiation of murine embryonic stem cells

Understanding the process of ex vivo embryonic stem (ES) cell differentiation is important for generating higher yields of desirable cell types or lineages and for understanding fundamental aspects of ES differentiation. We used DNA microarray analysis to investigate the differentiation of mouse ES cells cultured under three differentiation conditions. Embryoid body (EB) formation was compared to differentiation on surfaces coated with either gelatin (GEL) or matrigel (MAT). Based on the transcriptional patterns of a list of literature-based "stemness" genes, ES cell differentiation on the two coated surfaces appeared similar but not identical to EB differentiation. A notable difference was the GEL and MAT upregulation but EB downregulation of nine such stemness genes, which are related to cell adhesion and epithelial differentiation. Further, GEL and MAT differentiation showed higher expression of bone formation-related genes (Spp1, Csf1, Gsn, Bmp8b, Crlf1). Gene ontology analysis shows an increase in the expression of genes related to migration and cell structure in all three conditions. Overall, GEL and MAT conditions resulted in a more similar to each other transcriptional profile than to the EB condition, and such differences are apparently related to higher nutrient and metabolite gradients and limitations in the EB versus the GEL or MAT cultures.

Role of Jade-1 in the histone acetyltransferase (HAT) HBO1 complex

Regulation of global chromatin acetylation is important for chromatin remodeling. A small family of Jade proteins includes Jade-1L, Jade-2, and Jade-3, each bearing two mid-molecule tandem plant homology domain (PHD) zinc fingers. We previously demonstrated that the short isoform of Jade-1L protein, Jade-1, is associated with endogenous histone acetyltransferase (HAT) activity. It has been found that Jade-1L/2/3 proteins co-purify with a novel HAT complex, consisting of HBO1, ING4/5, and Eaf6. We investigated a role for Jade-1/1L in the HBO1 complex. When overexpressed individually, neither Jade-1/1L nor HBO1 affected histone acetylation. However, co-expression of Jade-1/1L and HBO1 increased acetylation of the bulk of endogenous histone H4 in epithelial cells in a synergistic manner, suggesting that Jade1/1L positively regulates HBO1 HAT activity. Conversely, small interfering RNA-mediated depletion of endogenous Jade resulted in reduced levels of H4 acetylation. Moreover, HBO1-mediated H4 acetylation activity was enhanced severalfold by the presence of Jade-1/1L in vitro. The removal of PHD fingers affected neither binding nor mutual Jade-1-HBO1 stabilization but completely abrogated the synergistic Jade-1/1L- and HBO1-mediated histone H4 acetylation in live cells and in vitro with reconstituted oligonucleosome substrates. Therefore, PHDs are necessary for Jade-1/1L-induced acetylation of nucleosomal histones by HBO1. In contrast to Jade-1/1L, the PHD zinc finger protein ING4/5 failed to synergize with HBO1 to promote histone acetylation. The physical interaction of ING4/5 with HBO1 occurred in the presence of Jade-1L or Jade-3 but not with the Jade-1 short isoform. In summary, this study demonstrates that Jade-1/1L are crucial co-factors for HBO1-mediated histone H4 acetylation.

Jade-1 inhibits Wnt signalling by ubiquitylating beta-catenin and mediates Wnt pathway inhibition by pVHL

The von Hippel-Lindau protein pVHL suppresses renal tumorigenesis in part by promoting the degradation of hypoxia-inducible HIF-alpha transcription factors; additional mechanisms have been proposed. pVHL also stabilizes the plant homeodomain protein Jade-1, which is a candidate renal tumour suppressor that may correlate with renal cancer risk. Here we show that Jade-1 binds the oncoprotein beta-catenin in Wnt-responsive fashion. Moreover, Jade-1 destabilizes wild-type beta-catenin but not a cancer-causing form of beta-catenin. Whereas the well-established beta-catenin E3 ubiquitin ligase component beta-TrCP ubiquitylates only phosphorylated beta-catenin, Jade-1 ubiquitylates both phosphorylated and non-phosphorylated beta-catenin and therefore regulates canonical Wnt signalling in both Wnt-off and Wnt-on phases. Thus, the different characteristics of beta-TrCP and Jade-1 may ensure optimal Wnt pathway regulation. Furthermore, pVHL downregulates beta-catenin in a Jade-1-dependent manner and inhibits Wnt signalling, supporting a role for Jade-1 and Wnt signalling in renal tumorigenesis. The pVHL tumour suppressor and the Wnt tumorigenesis pathway are therefore directly linked through Jade-1.

The Arabidopsis OBERON1 and OBERON2 genes encode plant homeodomain finger proteins and are required for apical meristem maintenance

Maintenance of the stem cell population located at the apical meristems is essential for repetitive organ initiation during the development of higher plants. Here, we have characterized the roles of OBERON1 (OBE1) and its paralog OBERON2 (OBE2), which encode plant homeodomain finger proteins, in the maintenance and/or establishment of the meristems in Arabidopsis. Although the obe1 and obe2 single mutants were indistinguishable from wild-type plants, the obe1 obe2 double mutant displayed premature termination of the shoot meristem, suggesting that OBE1 and OBE2 function redundantly. Further analyses revealed that OBE1 and OBE2 allow the plant cells to acquire meristematic activity via the WUSCHEL-CLAVATA pathway, which is required for the maintenance of the stem cell population, and they function parallel to the SHOOT MERISTEMLESS gene, which is required for preventing cell differentiation in the shoot meristem. In addition, obe1 obe2 mutants failed to establish the root apical meristem, lacking both the initial cells and the quiescent center. In situ hybridization revealed that expression of PLETHORA and SCARECROW, which are required for stem cell specification and maintenance in the root meristem, was lost from obe1 obe2 mutant embryos. Taken together, these data suggest that the OBE1 and OBE2 genes are functionally redundant and crucial for the maintenance and/or establishment of both the shoot and root meristems.

MYST opportunities for growth control: yeast genes illuminate human cancer gene functions

The MYST family of histone acetyltransferases (HATs) was initially defined by human genes with disease connections and by yeast genes identified for their role in epigenetic transcriptional silencing. Since then, many new MYST genes have been discovered through genetic and genomic approaches. Characterization of the complexes through which MYST proteins act, regions of the genome to which they are targeted and biological consequences when they are disrupted, all deepen the connections of MYST proteins to development, growth control and human cancers. Many of the insights into MYST family function have come from studies in model organisms. Herein, we review functions of two of the founding MYST genes, yeast SAS2 and SAS3, and the essential yeast MYST ESA1. Analysis of these genes in yeast has defined roles for MYST proteins in transcriptional activation and silencing, and chromatin-mediated boundary formation. They have further roles in DNA damage repair and nuclear integrity. The observation that MYST protein complexes share subunits with other HATs, histone deacetylases and other key nuclear proteins, many with connections to human cancers, strengthens the idea that coordinating distinct chromatin modifications is critical for regulation.

Cellular functions of TIP60

TIP60 was originally identified as a cellular acetyltransferase protein that interacts with HIV-1 Tat. As a consequence, the role of TIP60 in transcriptional regulation has been investigated intensively. Recent data suggest that TIP60 has more divergent functions than originally thought and roles for TIP60 in many processes, such as cellular signalling, DNA damage repair, cell cycle and checkpoint control and apoptosis are emerging. TIP60 is a tightly regulated transcriptional coregulator, acting in a large multiprotein complex for a range of transcription factors including androgen receptor, Myc, STAT3, NF-kappaB, E2F1 and p53. This usually involves recruitment of TIP60 acetyltransferase activities to chromatin. Additionally, in response to DNA double strand breaks, TIP60 is recruited to DNA lesions where it participates both in the initial as well as the final stages of repair. Here, we describe how TIP60 is a multifunctional enzyme involved in multiple nuclear transactions.

The Epc-N domain: a predicted protein-protein interaction domain found in select chromatin associated proteins

Background

An underlying tenet of the epigenetic code hypothesis is the existence of protein domains that can recognize various chromatin structures. To date, two major candidates have emerged: (i) the bromodomain, which can recognize certain acetylation marks and (ii) the chromodomain, which can recognize certain methylation marks.

Results

The Epc-N (Enhancer of Polycomb-N-terminus) domain is formally defined herein. This domain is conserved across eukaryotes and is predicted to form a right-handed orthogonal four-helix bundle with extended strands at both termini. The types of amino acid residues that define the Epc-N domain suggest a role in mediating protein-protein interactions, possibly specifically in the context of chromatin binding, and the types of proteins in which it is found (known components of histone acetyltransferase complexes) strongly suggest a role in epigenetic structure formation and/or recognition. There appear to be two major Epc-N protein families that can be divided into four unique protein subfamilies. Two of these subfamilies (I and II) may be related to one another in that subfamily I can be viewed as a plant-specific expansion of subfamily II. The other two subfamilies (III and IV) appear to be related to one another by duplication events in a primordial fungal-metazoan-mycetozoan ancestor. Subfamilies III and IV are further defined by the presence of an evolutionarily conserved five-center-zinc-binding motif in the loop connecting the second and third helices of the four-helix bundle. This motif appears to consist of a PHD followed by a mononuclear Zn knuckle, followed by a PHD-like derivative, and will thus be referred to as the PZPM. All non-Epc-N proteins studied thus far that contain the PZPM have been implicated in histone methylation and/or gene silencing. In addition, an unusual phyletic distribution of Epc-N-containing proteins is observed.

Conclusion

The data suggest that the Epc-N domain is a protein-protein interaction module found in chromatin associated proteins. It is possible that the Epc-N domain serves as a direct link between histone acetylation and methylation statuses. The unusual phyletic distribution of Epc-N-containing proteins may provide a conduit for future insight into how different organisms form, perceive and respond to epigenetic information.

ING tumor suppressor proteins are critical regulators of chromatin acetylation required for genome expression and perpetuation

Members of the ING family of tumor suppressors regulate cell cycle progression, apoptosis, and DNA repair as important cofactors of p53. ING1 and ING3 are stable components of the mSin3A HDAC and Tip60/NuA4 HAT complexes, respectively. We now report the purification of the three remaining human ING proteins. While ING2 is in an HDAC complex similar to ING1, ING4 associates with the HBO1 HAT required for normal progression through S phase and the majority of histone H4 acetylation in vivo. ING5 fractionates with two distinct complexes containing HBO1 or nucleosomal H3-specific MOZ/MORF HATs. These ING5 HAT complexes interact with the MCM helicase and are essential for DNA replication to occur during S phase. Our data also indicate that ING subunits are crucial for acetylation of chromatin substrates. Since INGs, HBO1, and MOZ/MORF contribute to oncogenic transformation, the multisubunit assemblies characterized here underscore the critical role of epigenetic regulation in cancer development.

Génétique des tumeurs endocrines

Major advances have been made in the understanding of the genetic mechanisms underlying endocrine tumorigenesis, through the study of several syndromes of genetic predisposition and the identification of the genes involved. The syndrome of type 1 multiple endocrine neoplasia (MEN-1) is one of the best known; this autosomal dominant hereditary syndrome predisposes to the development of endocrine tumors of the pituitary, the parathyroids, the foregut and the adrenals. The responsible gene, known as MEN-1, encodes an original protein, menin, involved in several major cellular functions, such as the control of cell proliferation and differentiation. Type 2 multiple endocrine neoplasia (MEN-2) is an autosomal dominant hereditary syndrome associated with the development of medullary carcinomas of the thyroid, pheochromocytomas and hyperparathyroidism; the corresponding gene, RET, encodes a transmembrane receptor with tyrosine kinase activity. Endocrine tumors are also associated with non Hippel-Lindau disease and with phacomatoses, such as type 1 neurofibromatosis and tuberous sclerosis. Finally, isolated familial syndromes of endocrine tumors have been described: isolated familial hyperparathyroidism type II (HRPT2), associated with alterations in a gene coding for an original protein, parafibromin, or isolated familial syndromes of pheochromocytomas and paragangliomas (PRG) associated with mutations in the genes SDHB, SDHC or SDHD, which encode succinate-dehydrogenase subunits. The understanding of the genetic mechanisms underlying these syndromes of predisposition is essential for the diagnosis and management of these patients and their family; it also gives insight on the molecular mechanisms of endocrine tumorigenesis.

Jade-1, a candidate renal tumor suppressor that promotes apoptosis

Medical therapies are lacking for advanced renal cancer, so there is a great need to understand its pathogenesis. Most renal cancers have defects in the von Hippel-Lindau tumor suppressor pVHL. The mechanism by which pVHL protein functions in renal tumor suppression remains unclear. Jade-1 is a short-lived, kidney-enriched transcription factor that is stabilized by direct interaction with pVHL. Loss of Jade-1 stabilization by pVHL correlates with renal cancer risk, making the relationship between Jade-1 and renal cancer compelling. We report that Jade-1 expression was barely detectable in all tested renal cancer cell lines, regardless of VHL status. Strikingly, proteasome inhibitor treatment increased endogenous Jade-1 expression up to 10-fold. Jade-1 inhibited renal cancer cell growth, colony formation, and tumor formation in nude mice. Intriguingly, Jade-1 also affected the pattern of cell growth in monolayer culture and 3D culture. Jade-1 increased apoptosis by 40-50% and decreased levels of antiapoptotic Bcl-2. Antisense Jade-1-expressing cells confirmed these results. Therefore, Jade-1 may suppress renal cancer cell growth in part by increasing apoptosis. Jade-1 may represent a proapoptotic barrier to proliferation that must be overcome generally in renal cancer, perhaps initially by pVHL inactivation and subsequently by increased proteasomal activity. Therefore, Jade-1 may be a renal tumor suppressor.