ZXDC, a novel zinc finger protein that binds CIITA and activates MHC gene transcription

Glomerular transcriptomics predicts long term outcome and identifies therapeutic strategies for patients with assumed benign IgA nephropathy

Some patients diagnosed with benign IgA nephropathy (IgAN) develop a progressive clinical course, not predictable by known clinical or histopathological parameters. To assess if gene expression can differentiate between progressors and non-progressors with assumed benign IgAN, we tested microdissected glomeruli from archival kidney biopsy sections from adult patients with stable clinical remission (21 non-progressors) or from 15 patients that had undergone clinical progression within a 25-year time frame. Based on 1 240 differentially expressed genes from patients with suitable sequencing results, we identified eight IgAN progressor and nine non-progressor genes using a two-component classifier. These genes, including APOL5 and ZXDC, predicted disease progression with 88% accuracy, 75% sensitivity and 100% specificity on average 21.6 years before progressive disease was clinically documented. APOL lipoproteins are associated with inflammation, autophagy and kidney disease while ZXDC is a zinc-finger transcription factor modulating adaptive immunity. Ten genes from our transcriptomics data overlapped with an external genome wide association study dataset, although the gene set enrichment test was not statistically significant. We also identified 45 drug targets in the DrugBank database, including angiotensinogen, a target of sparsentan (dual antagonist of the endothelin type A receptor and the angiotensin II type 1 receptor) currently investigated for IgAN treatment. Two validation cohorts were used for substantiating key results, one by immunohistochemistry and the other by nCounter technology. Thus, glomerular mRNA sequencing from diagnostic kidney biopsies from patients with assumed benign IgAN can differentiate between future progressors and non-progressors at the time of diagnosis.

ZXDC enhances cervical cancer metastasis through IGF2BP3-mediated activation of RhoA/ROCK signaling

Metastasis in cervical cancer (CC) has a significant negative impact on patient survival, highlighting the urgent need for investigation in this area. In this study, we identified significant overexpression of zinc finger, X-linked, duplicated family member C (ZXDC) in CC tissue with metastasis, which correlates with poor outcomes for CC patients. We observed that overexpression of ZXDC promotes, while silencing of ZXDC inhibits the metastasis of CC cells both in vitro and in vivo. Additionally, our research demonstrated that ZXDC activated RhoA/ROCK signaling pathway, leading to enhanced cytoskeleton remodeling in CC cells. Besides, we found that IGF2BP3 plays an essential role in the activation of ZXDC on the RhoA/ROCK signaling pathway by stabilizing RhoA mRNA. These findings reveal a mechanism whereby ZXDC promotes the cervical cancer metastasis by targeting IGF2BP3/RhoA/ROCK pathway.

CircZXDC Promotes Vascular Smooth Muscle Cell Transdifferentiation via Regulating miRNA-125a-3p/ABCC6 in Moyamoya Disease

Moyamoya disease (MMD) is an occlusive, chronic cerebrovascular disease affected by genetic mutation and the immune response. Furthermore, vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) participate in the neointima of MMD, but the etiology and pathophysiological changes in MMD vessels remain largely unknown. Therefore, we established the circZXDC (ZXD family zinc finger C)-miR-125a-3p-ABCC6 (ATP-binding cassette subfamily C member 6) axis from public datasets and online tools based on "sponge-like" interaction mechanisms to investigate its possible role in VSMCs. The results from a series of in vitro experiments, such as dual luciferase reporter assays, cell transfection, CCK-8 assays, Transwell assays, and Western blotting, indicate a higher level of circZXDC in the MMD plasma, especially in those MMD patients with the RNF213 mutation. Moreover, circZXDC overexpression results in a VSMC phenotype switching toward a synthetic status, with increased proliferation and migration activity. CircZXDC sponges miR-125a-3p to increase ABCC6 expression, which induces ERS (endoplasmic reticulum stress), and subsequently regulates VSMC transdifferentiation from the contractive phenotype to the synthetic phenotype, contributing to the intima thickness of MMD vessels. Our findings provide insight into the pathophysiological mechanisms of MMD and indicate that the circZXDC-miR-125a-3p-ABCC6 axis plays a pivotal role in the progression of MMD. Furthermore, circZXDC might be a diagnostic biomarker and an ABCC6-specific inhibitor and has the potential to become a promising therapeutic option for MMD.

Transcription factor EB enhances autophagy and ameliorates palmitate-induced insulin resistance at least partly via upregulating AMPK activity in skeletal muscle cells

This study aimed to elucidate the role of transcription factor EB (TFEB) in protecting C2C12 myotubes against palmitate (PA)-induced insulin resistance (IR) and explored its mechanism associated with autophagy. PA treatment significantly decreased insulin sensitivity in myotubes and downregulated TFEB protein expression. TFEB overexpression significantly reversed the PA-suppressed glucose transporter 4 (GLUT4) protein expression and improved intracellular glucose uptake and consumption, and also alleviated the decrease of autophagy markers induced by PA. The effect of TFEB overexpression on GLUT4 was also abolished by the autophagy inhibitor 3-MA. In addition, AMPKɑ2-DN inhibited or abolished the effects of TFEB overexpression on upregulation of GLUT4 and PA-induced decrease of autophagy marker expressions. Taken together, our data demonstrated that upregulation of TFEB improved PA-induced IR in C2C12 myotubes by enhancing autophagy and upregulating AMPK activity. TFEB, as a critical regulator of glucose homeostasis in skeletal muscle cells, may be a potential therapeutic target for IR and Type 2 diabetes.

Germline genetic factors in the pathogenesis of myeloproliferative neoplasms

Myeloproliferative neoplasms (MPN) are clonal hematological malignancies that lead to overproduction of mature myeloid cells. They are due to acquired mutations in genes encoding for AK2, MPL and CALR that result in the activation of the cytokine receptor/JAK2 signaling pathway. In addition, it exists germline variants that can favor the initiation of the disease or may affect its phenotype. First, they can be common risk alleles, which correspond to frequent single nucleotide variants present in control population and that contribute to the development of either sporadic or familial MPN. Second, some variants predispose to the onset of MPN with a higher penetrance and lead to familial clustering of MPN. Finally, some extremely rare genetic variants can induce MPN-like hereditary disease. We will review these different subtypes of germline genetic variants and discuss how they impact the initiation and/or development of the MPN disease.

Whole-exome sequencing identifies novel candidate predisposition genes for familial polycythemia vera

Background

Polycythemia vera (PV), characterized by massive production of erythrocytes, is one of the myeloproliferative neoplasms. Most patients carry a somatic gain-of-function mutation in JAK2, c.1849G > T (p.Val617Phe), leading to constitutive activation of JAK-STAT signaling pathway. Familial clustering is also observed occasionally, but high-penetrance predisposition genes to PV have remained unidentified.

Results

We studied the predisposition to PV by exome sequencing (three cases) in a Finnish PV family with four patients. The 12 shared variants (maximum allowed minor allele frequency <0.001 in Finnish population in ExAC database) predicted damaging in silico and absent in an additional control set of over 500 Finns were further validated by Sanger sequencing in a fourth affected family member. Three novel predisposition candidate variants were identified: c.1254C > G (p.Phe418Leu) in ZXDC, c.1931C > G (p.Pro644Arg) in ATN1, and c.701G > A (p.Arg234Gln) in LRRC3. We also observed a rare, predicted benign germline variant c.2912C > G (p.Ala971Gly) in BCORL1 in all four patients. Somatic mutations in BCORL1 have been reported in myeloid malignancies. We further screened the variants in eight PV patients in six other Finnish families, but no other carriers were found.

Conclusions

Exome sequencing provides a powerful tool for the identification of novel variants, and understanding the familial predisposition of diseases. This is the first report on Finnish familial PV cases, and we identified three novel candidate variants that may predispose to the disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s40246-017-0102-x) contains supplementary material, which is available to authorized users.

Disease Variant Landscape of a Large Multiethnic Population of Moyamoya Patients by Exome Sequencing

Moyamoya disease (MMD) is a rare disorder characterized by cerebrovascular occlusion and development of hemorrhage-prone collateral vessels. Approximately 10-12% of cases are familial, with a presumed low penetrance autosomal dominant pattern of inheritance. Diagnosis commonly occurs only after clinical presentation. The recent identification of the RNF213 founder mutation (p.R4810K) in the Asian population has made a significant contribution, but the etiology of this disease remains unclear. To further develop the variant landscape of MMD, we performed high-depth whole exome sequencing of 125 unrelated, predominantly nonfamilial, ethnically diverse MMD patients in parallel with 125 internally sequenced, matched controls using the same exome and analysis platform. Three subpopulations were established: Asian, Caucasian, and non-RNF213 founder mutation cases. We provided additional support for the previously observed RNF213 founder mutation (p.R4810K) in Asian cases (P = 6.01×10(-5)) that was enriched among East Asians compared to Southeast Asian and Pacific Islander cases (P = 9.52×10(-4)) and was absent in all Caucasian cases. The most enriched variant in Caucasian (P = 7.93×10(-4)) and non-RNF213 founder mutation (P = 1.51×10(-3)) cases was ZXDC (p.P562L), a gene involved in MHC Class II activation. Collapsing variant methodology ranked OBSCN, a gene involved in myofibrillogenesis, as most enriched in Caucasian (P = 1.07×10(-4)) and non-RNF213 founder mutation cases (P = 5.31×10(-5)). These findings further support the East Asian origins of the RNF213 (p.R4810K) variant and more fully describe the genetic landscape of multiethnic MMD, revealing novel, alternative candidate variants and genes that may be important in MMD etiology and diagnosis.

The Orphan Nuclear Receptor TLX Is an Enhancer of STAT1-Mediated Transcription and Immunity to Toxoplasma gondii

The protozoan parasite, Toxoplasma, like many intracellular pathogens, suppresses interferon gamma (IFN-γ)-induced signal transducer and activator of transcription 1 (STAT1) activity. We exploited this well-defined host–pathogen interaction as the basis for a high-throughput screen, identifying nine transcription factors that enhance STAT1 function in the nucleus, including the orphan nuclear hormone receptor TLX. Expression profiling revealed that upon IFN-γ treatment TLX enhances the output of a subset of IFN-γ target genes, which we found is dependent on TLX binding at those loci. Moreover, infection of TLX deficient mice with the intracellular parasite Toxoplasma results in impaired production of the STAT1-dependent cytokine interleukin-12 by dendritic cells and increased parasite burden in the brain during chronic infection. These results demonstrate a previously unrecognized role for this orphan nuclear hormone receptor in regulating STAT1 signaling and host defense and reveal that STAT1 activity can be modulated in a context-specific manner by such “modifiers.”

Exploitation of the parasite Toxoplasma gondii identifies the host orphan nuclear hormone receptor TLX as a key enhancer of STAT1-dependent immune signaling and host defense.

Immune responses are orchestrated by a diverse array of secreted ligands, yet the downstream transcriptional responses are coordinated by a relatively small set of key transcription factors, including nuclear factor kappa B (NF-κB) and signal transducers and activators of transcription (STATs). The molecular mechanisms that tailor the output of these immune signaling pathways to generate cell-, tissue-, or context-specific responses are poorly understood. In this study, we exploit a host–pathogen interaction, Toxoplasma gondii infection in mice, using a genetic screen to identify host factors that overcome parasite suppression of STAT1 signaling. We show that the orphan nuclear receptor TLX, a key regulator of brain development, enhances expression of a subset of STAT1-dependent genes in response to IFN-γ stimulation. Through genetic and pharmacological studies, we show that endogenous TLX function is required for triggering appropriate responses to IFN-γ in astrocytes. Moreover, we found that genetic disruption of TLX in mice impairs their ability to mount an effective immune response and control T. gondii infection in the brain. These data suggest that natural or synthetic ligands for TLX might be effective tools for modulating immune responses, particularly in the brain where TLX expression is highest.

Identification of potential serum proteomic biomarkers for clear cell renal cell carcinoma

Objective

To investigate discriminating protein patterns and serum biomarkers between clear cell renal cell carcinoma (ccRCC) patients and healthy controls, as well as between paired pre- and post-operative ccRCC patients.

Methods

We used magnetic bead-based separation followed by matrix-assisted laser desorption ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS) to identify patients with ccRCC. A total of 162 serum samples were analyzed in this study, among which there were 58 serum samples from ccRCC patients, 40 from additional paired pre- and post-operative ccRCC patients (n = 20), and 64 from healthy volunteers as healthy controls. ClinProTools software identified several distinct markers between ccRCC patients and healthy controls, as well as between pre- and post-operative patients.

Results

Patients with ccRCC could be identified with a mean sensitivity of 88.38% and a mean specificity of 91.67%. Of 67 m/z peaks that differed among the ccRCC, healthy controls, pre- and post-operative ccRCC patients, 24 were significantly different (P<0.05). Three candidate peaks, which were upregulated in ccRCC group and showed a tendency to return to healthy control values after surgery, were identified as peptide regions of RNA-binding protein 6 (RBP6), tubulin beta chain (TUBB), and zinc finger protein 3 (ZFP3) with the m/z values of 1466.98, 1618.22, and 5905.23, respectively.

Conclusion

MB-MALDI-TOF-MS method could generate serum peptidome profiles of ccRCC, and provide a new approach to identify potential biomarkers for diagnosis as well as prognosis of this malignancy.

Population and genomic lessons from genetic analysis of two Indian populations

Indian demographic history includes special features such as founder effects, interpopulation segregation, complex social structure with a caste system and elevated frequency of consanguineous marriages. It also presents a higher frequency for some rare mendelian disorders and in the last two decades increased prevalence of some complex disorders. Despite the fact that India represents about one-sixth of the human population, deep genetic studies from this terrain have been scarce. In this study, we analyzed high-density genotyping and whole-exome sequencing data of a North and a South Indian population. Indian populations show higher differentiation levels than those reported between populations of other continents. In this work, we have analyzed its consequences, by specifically assessing the transferability of genetic markers from or to Indian populations. We show that there is limited genetic marker portability from available genetic resources such as HapMap or the 1,000 Genomes Project to Indian populations, which also present an excess of private rare variants. Conversely, tagSNPs show a high level of portability between the two Indian populations, in contrast to the common belief that North and South Indian populations are genetically very different. By estimating kinship from mates and consanguinity in our data from trios, we also describe different patterns of assortative mating and inbreeding in the two populations, in agreement with distinct mating preferences and social structures. In addition, this analysis has allowed us to describe genomic regions under recent adaptive selection, indicating differential adaptive histories for North and South Indian populations. Our findings highlight the importance of considering demography for design and analysis of genetic studies, as well as the need for extending human genetic variation catalogs to new populations and particularly to those with particular demographic histories.

Identification of cellular proteins that interact with human cytomegalovirus immediate-early protein 1 by protein array assay

Human cytomegalovirus (HCMV) gene expression during infection is characterized as a sequential process including immediate-early (IE), early (E), and late (L)-stage gene expression. The most abundantly expressed gene at the IE stage of infection is the major IE (MIE) gene that produces IE1 and IE2. IE1 has been the focus of study because it is an important protein, not only for viral gene expression but also for viral replication. It is believed that IE1 plays important roles in viral gene regulation by interacting with cellular proteins. In the current study, we performed protein array assays and identified 83 cellular proteins that interact with IE1. Among them, seven are RNA-binding proteins that are important in RNA processing; more than half are nuclear proteins that are involved in gene regulations. Tumorigenesis-related proteins are also found to interact with IE1, implying that the role of IE1 in tumorigenesis might need to be reevaluated. Unexpectedly, cytoplasmic proteins, such as Golgi autoantigen and GGA1 (both related to the Golgi trafficking protein), are also found to be associated with IE1. We also employed a coimmunoprecipitation assay to test the interactions of IE1 and some of the proteins identified in the protein array assays and confirmed that the results from the protein array assays are reliable. Many of the proteins identified by the protein array assay have not been previously reported. Therefore, the functions of the IE1-protein interactions need to be further explored in the future.

The zinc finger transcription factor ZXDC activates CCL2 gene expression by opposing BCL6-mediated repression

The zinc finger X-linked duplicated (ZXD) family of transcription factors has been implicated in regulating transcription of major histocompatibility complex class II genes in antigen presenting cells; roles beyond this function are not yet known. The expression of one gene in this family, ZXD family zinc finger C (ZXDC), is enriched in myeloid lineages and therefore we hypothesized that ZXDC may regulate myeloid-specific gene expression. Here we demonstrate that ZXDC regulates genes involved in myeloid cell differentiation and inflammation. Overexpression of the larger isoform of ZXDC, ZXDC1, activates expression of monocyte-specific markers of differentiation and synergizes with phorbol 12-myristate 13-acetate (which causes differentiation) in the human leukemic monoblast cell line U937. To identify additional gene targets of ZXDC1, we performed gene expression profiling which revealed multiple inflammatory gene clusters regulated by ZXDC1. Using a combination of approaches we show that ZXDC1 activates transcription of a gene within one of the regulated clusters, chemokine (C-C motif) ligand 2 (CCL2; monocyte chemoattractant protein 1; MCP1) via a previously defined distal regulatory element. Further, ZXDC1-dependent up-regulation of the gene involves eviction of the transcriptional repressor B-cell CLL/lymphoma 6 (BCL6), a factor known to be important in resolving inflammatory responses, from this region of the promoter. Collectively, our data show that ZXDC1 is a regulator in the process of myeloid function and that ZXDC1 is responsible for Ccl2 gene de-repression by BCL6.

Novel gene markers of immunosuppressive chemicals in mouse lymph node assay

The murine local lymph node assay (LLNA) is an immunologically based test of the sensitizing potential of immunotoxicants, but also evaluates immunosuppressive potential with good sensitivity and specificity. We conducted the LLNA with calcineurin inhibitors (tacrolimus and cyclosporin A), antimetabolites (methotrexate and azathioprine), steroids (dexamethasone and prednisolone), and an alkylator (cyclophosphamide). We performed a comprehensive analysis of results of gene expression in lymph nodes obtained in the LLNA using a highly sensitive DNA chip, 3D-Gene™, and the quantitative reverse transcription-polymerase chain reaction (qPCR). Zfp459 expression increased in all animals treated with immunosuppressive chemicals. Ltf, Cbll1 and Lias expression changed specifically in response to the calcineurin inhibitors, Fmo2 and 9630033F20Rik in response to the antimetabolites, Krt8, Gjb1, Hmha1 and Sfrs7 in response to the steroids, and Gbp1 and Mup5 in response to the alkylator. Therefore, these genes were considered novel markers for immunosuppression and their expression could be used to evaluate the mechanism of action of immunosuppressive chemicals.

Interplay of chemical neurotransmitters regulates developmental increase in electrical synapses

Coupling of neurons by electrical synapses (gap junctions) transiently increases in the mammalian CNS during development. We report here that the developmental increase in neuronal gap junction coupling and expression of connexin 36 (Cx36; neuronal gap junction protein) are regulated by an interplay between the activity of group II metabotropic glutamate receptors (mGluRs) and GABA(A) receptors. Specifically, using dye coupling, electrotonic coupling, Western blots and small interfering RNA in the rat and mouse hypothalamus and cortex in vivo and in vitro, we demonstrate that activation of group II mGluRs augments, and inactivation prevents, the developmental increase in neuronal gap junction coupling and Cx36 expression. However, changes in GABA(A) receptor activity have the opposite effects. The regulation by group II mGluRs is via cAMP/PKA-dependent signaling, and regulation by GABA(A) receptors is via Ca(2+)/PKC-dependent signaling. Furthermore, the receptor-mediated upregulation of Cx36 requires a neuron-restrictive silencer element in the Cx36 gene promoter, and the downregulation involves the 3'-untranslated region of the Cx36 mRNA, as shown using reverse-transcription quantitative real-time PCR and luciferase reporter activity analysis. In addition, the methyl thiazolyl tetrazolium analysis indicates that mechanisms for the developmental increase in neuronal gap junction coupling directly control the death/survival mechanisms in developing neurons. Together, the results suggest a multitiered strategy for chemical synapses in developmental regulation of electrical synapses.

Isolation and characterization of a novel zinc finger gene, ZNFD, activating AP1(PMA) transcriptional activities

ZFPs (Zinc Finger Proteins) play important roles in various cellular functions, including transcriptional activation, transcriptional repression, cell proliferation, and development. C(2)H(2) (Cys-Cys-His-His motif) ZFPs are the most abundant proteins among the founding members of the ZFP super family in eukaryotes. In this study, we isolate a novel C(2)H(2) ZNF (Zinc Finger) gene ZNFD. It contains an ORF (Open Reading Frame) with a length of 990 bp, encoding 329 amino acids. The predicted protein contains a C(2)H(2) zinc finger. RT-PCR analysis in 18 human adult tissues indicated that it was expressed in five human adult tissues. Green fluorescence protein localization analysis showed that human ZNFD was located in the nucleus of Hela cells. Overexpression of ZNFD in the COS7 cells activates the transcriptional activities of AP1(PMA) (Activator of protein 1, that responds specifically to phorbol ester). Together the data indicate that ZNFD is probably a new type of C(2)H(2) ZFP and the ZNFD protein may act as a transcriptional activator in PKC (protein kinase C) signal pathway to mediate cellular functions.

An N- and C-terminal truncated isoform of zinc finger X-linked duplicated C protein represses MHC class II transcription

The zinc finger X-linked duplicated A (ZXDA) and ZXDC proteins are both required for robust transcription of major histocompatibility complex class II (MHC II) genes. Aside from the full length ZXDC mRNA transcript, at least one additional mRNA is produced by the ZXDC gene, in which transcription initiates within the first exon and terminates within the seventh intron. The protein product produced from this transcript, which we have named ZXDC2, is truncated on both the N- and C-terminus. We demonstrate here that ZXDC2 functions to repress MHC II transcription induced in HeLa cells treated with IFN-gamma. We further demonstrate that ZXDC2 interacts with both ZXDA and ZXDC, suggesting a mechanism by which ZXDC2 may inhibit MHC II transcription. These studies not only provide additional support for the role of ZXD proteins in regulating MHC II transcription, but also demonstrate a unique mechanism for the synthesis of a mRNA isoform.

Understanding diversity of human innate immunity receptors: analysis of surface features of leucine-rich repeat domains in NLRs and TLRs

BACKGROUND

The human innate immune system uses a system of extracellular Toll-like receptors (TLRs) and intracellular Nod-like receptors (NLRs) to match the appropriate level of immune response to the level of threat from the current environment. Almost all NLRs and TLRs have a domain consisting of multiple leucine-rich repeats (LRRs), which is believed to be involved in ligand binding. LRRs, found also in thousands of other proteins, form a well-defined "horseshoe"-shaped structural scaffold that can be used for a variety of functions, from binding specific ligands to performing a general structural role. The specific functional roles of LRR domains in NLRs and TLRs are thus defined by their detailed surface features. While experimental crystal structures of four human TLRs have been solved, no structure data are available for NLRs.

RESULTS

We report a quantitative, comparative analysis of the surface features of LRR domains in human NLRs and TLRs, using predicted three-dimensional structures for NLRs. Specifically, we calculated amino acid hydrophobicity, charge, and glycosylation distributions within LRR domain surfaces and assessed their similarity by clustering. Despite differences in structural and genomic organization, comparison of LRR surface features in NLRs and TLRs allowed us to hypothesize about their possible functional similarities. We find agreement between predicted surface similarities and similar functional roles in NLRs and TLRs with known agonists, and suggest possible binding partners for uncharacterized NLRs.

CONCLUSION

Despite its low resolution, our approach permits comparison of molecular surface features in the absence of crystal structure data. Our results illustrate diversity of surface features of innate immunity receptors and provide hints for function of NLRs whose specific role in innate immunity is yet unknown.

Sumoylation of the zinc finger protein ZXDC enhances the function of its transcriptional activation domain

The transcription of major histocompatibility complex class II (MHC II) genes is dependent on the co-activator protein class II trans-activator (CIITA). We have recently identified a protein known as zinc finger X-linked duplicated family member C (ZXDC) that, along with its binding partner ZXDA, forms a complex that interacts with CIITA and regulates MHC II transcription. Western blot analysis with anti-ZXDC antibodies identified two species of the ZXDC protein, one migrating near its predicted molecular mass and one with slower electrophoretic mobility. We report here that the slower migrating form is the result of sumoylation at a single lysine residue within the transcriptional activation domain of ZXDC. Three SUMO proteins (SUMO-1, -2 and -3) can modify the ZXDC protein. Multiple SUMO E3 ligase enzymes and HDAC4 can facilitate ZXDC sumoylation, and one ligase, PIASy, interacts with a specific region of the ZXDC protein. We found that sumoylation does not appear to disrupt or modulate the interaction of ZXDC with its binding partners. Rather, sumoylation of ZXDC is required for full activity of the transcriptional activation domain. Our findings suggest that sumoylation is an important regulator of ZXDC.

Fasting-induced changes in ECL cell gene expression

Gastric enterochromaffin-like (ECL) cells release histamine in response to food because of elevation of gastrin and neural release of pituitary adenylate cyclase-activating peptide (PACAP). Acid secretion is at a basal level in the absence of food but is rapidly stimulated with feeding. Rats fasted for 24 h showed a significant decrease of mucosal histamine despite steady-state expression of the histamine-synthesizing enzyme histidine decarboxylase (HDC). Comparative transcriptomal analysis using gene expression oligonucleotide microarrays of 95% pure ECL cells from fed and 24-h fasted rats, thereby eliminating mRNA contamination from other gastric mucosal cell types, identified significantly increased gene expression of the enzymes histidase and urocanase catabolizing the HDC substrate L-histidine but significantly decreased expression of the cellular L-histidine uptake transporter SN2 and of the vesicular monoamine transporter 2 (VMAT-2) responsible for histamine uptake into secretory vesicles. This was confirmed by reverse transcriptase-quantitative polymerase chain reaction of gastric fundic mucosal samples from fed and 24-h fasted rats. The decrease of VMAT-2 gene expression was also shown by a decrease in VMAT-2 protein content in protein extracts from fed and 24-h fasted rats compared with equal amounts of HDC protein and Na-K-ATPase alpha(1)-subunit protein content. These results indicate that rat gastric ECL cells regulate their histamine content during 24-h fasting not by a change in HDC gene or protein expression but by regulation of substrate concentration for HDC and a decreased histamine secretory pool.

The zinc finger proteins ZXDA and ZXDC form a complex that binds CIITA and regulates MHC II gene transcription

The transcription of major histocompatibility complex class II (MHC II) genes depends critically upon the activity of the class II trans-activator (CIITA) protein. We previously described a novel CIITA-binding protein named zinc finger X-linked duplicated family member C (ZXDC) that contributes to the activity of CIITA and the transcription of MHC II genes. Here, we examined the contribution of a closely related family member of ZXDC, the ZXDA protein, to MHC II gene transcription. ZXDA has a domain organization similar to ZXDC, containing ten zinc fingers and a transcriptional activation domain. Knockdown and overexpression of ZXDA demonstrated its importance in the transcriptional activation of MHC II genes. We found that ZXDA and ZXDC can self-associate, and also form a complex with each other. The regions of the two proteins that contain zinc fingers mediate these interactions. Importantly, we found that the ZXDA-ZXDC complex interacts with CIITA, rather than either protein alone. Given our additional finding that ZXDC is present at MHC II promoters in HeLa cells, prior to and after treatment with IFN-gamma, it appears that ZXDA and ZXDC form an important regulatory complex for MHC II gene transcription.