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At least 667 records · Page 37Linked to original sources
PubMed2004

A role for extra macrochaetae downstream of Notch in follicle cell differentiation.

The Drosophila ovary provides a model system for studying the mechanisms that regulate the differentiation of somatic stem cells into specific cell types. Ovarian somatic stem cells produce follicle cells, which undergo a binary choice during early differentiation. They can become either epithelial cells that surround the germline to form an egg chamber ('main body cells') or a specialized cell lineage found at the poles of egg chambers. This lineage goes on to make two cell types: polar cells and stalk cells. To better understand how this choice is made, we carried out a screen for genes that affect follicle cell fate specification or differentiation. We identified extra macrochaetae (emc), which encodes a helix-loop-helix protein, as a downstream effector of Notch signaling in the ovary. EMC is expressed in proliferating cells in the germarium, as well as in the main body follicle cells. EMC expression in the main body cells is Notch dependent, and emc mutant cells located on the main body failed to differentiate. EMC expression is reduced in the precursors of the polar and stalk cells, and overexpression of EMC caused dramatic egg chamber fusions, indicating that EMC is a negative regulator of polar and/or stalk cells. EMC and Notch were both required in the main body cells for expression of Eyes Absent (EYA), a negative regulator of polar and stalk cell fate. We propose that EMC functions downstream of Notch and upstream of EYA to regulate main body cell fate specification and differentiation.

Animals↗
PubMed2005

Commissural neuron identity is specified by a homeodomain protein, Mbh1, that is directly downstream of Math1.

Proneural basic helix-loop-helix (bHLH) proteins are key regulators of neurogenesis. However, downstream target genes of the bHLH proteins remain poorly defined. Mbh1 confers commissural neuron identity in the spinal cord. Enhancer analysis using transgenic mice revealed that Mbh1 expression required an E-box 3' of the Mbh1 gene. Mbh1 expression was lost in Math1 knockout mice, whereas misexpression of Math1 induced ectopic expression of Mbh1. Moreover, Math1 bound the Mbh1 enhancer containing the E-box in vivo and activated gene expression. Generation of commissural neurons by Math1 was inhibited by a dominant negative form of Mbh1. These findings indicate that Mbh1 is necessary and sufficient for the specification of commissural neurons, as a direct downstream target of Math1.

Animals↗
PubMed2005

Comparative analysis of genes downstream of the Hoxd cluster in developing digits and external genitalia.

Mammalian Hox genes encode transcription factors that are crucial for proper morphogenesis along the various body axes. Despite their extensive structural and functional characterization, the nature of their target genes remains elusive. We have addressed this question by using DNA microarrays to screen for genes whose expression in developing distal forelimbs and genital eminences was significantly modified in the absence of the full Hoxd gene complement. This comparative approach not only identified specific candidate genes, but also allowed the examination of whether a similar Hox expression pattern in distinct tissues leads to the modulation of the same or different downstream genes. We report here a set of potential target genes, most of which were not previously known to play a role in the early stages of either limb or genital bud development. Interestingly, we find that the majority of these candidate genes are differentially expressed in both structures, although often at different times. This supports the idea that both appendices involve similar genetic controls, both upstream and downstream of the Hox gene family. These results highlight the surprising mechanistic relationship between these rather different body parts and suggest a common developmental strategy to build up the most distal appendicular structures of the body, i.e. the digits and the penis/clitoris.

Animals↗
PubMed2005

Zebrafish vps33b, an ortholog of the gene responsible for human arthrogryposis-renal dysfunction-cholestasis syndrome, regulates biliary development downstream of the onecut transcription factor hnf6.

Arthrogryposis-renal dysfunction-cholestasis syndrome (ARC) is a rare cause of cholestasis in infants. Causative mutations in VPS33B, a gene that encodes a Class C vacuolar sorting protein, have recently been reported in individuals with ARC. We have identified a zebrafish vps33b-ortholog that is expressed in developing liver and intestine. Knockdown of vps33b causes bile duct paucity and impairs intestinal lipid absorption, thus phenocopying digestive defects characteristic of ARC. By contrast, neither motor axon nor kidney epithelial defects typically seen in ARC could be identified in vps33b-deficient larvae. Biliary defects in vps33b-deficient zebrafish larvae closely resemble the bile duct paucity associated with knockdown of the onecut transcription factor hnf6. Consistent with this, reduced vps33b expression was evident in hnf6-deficient larvae and in larvae with mutation of vhnf1, a downstream target of hnf6. Zebrafish vhnf1, but not hnf6, increases vps33b expression in zebrafish embryos and in mammalian liver cells. Electrophoretic mobility shift assays suggest that this regulation occurs through direct binding of vHnf1 to the vps33b promoter. These findings identify vps33b as a novel downstream target gene of the hnf6/vhnf1 pathway that regulates bile duct development in zebrafish. Furthermore, they show that tissue-specific roles for genes that regulate trafficking of intracellular proteins have been modified during vertebrate evolution.

Animals↗
PubMed2006

Dachs: an unconventional myosin that functions downstream of Fat to regulate growth, affinity and gene expression in Drosophila.

The dachs gene was first identified almost a century ago based on its requirements for appendage growth, but has been relatively little studied. Here, we describe the phenotypes of strong dachs mutations, report the cloning of the dachs gene, characterize the localization of Dachs protein, and investigate the relationship between Dachs and the Fat pathway. Mutation of dachs reduces, but does not abolish, the growth of legs and wings. dachs encodes an unconventional myosin that preferentially localizes to the membrane of imaginal disc cells. dachs mutations suppress the effects of fat mutations on gene expression, cell affinity and growth in imaginal discs. Dachs protein localization is influenced by Fat, Four-jointed and Dachsous, consistent with its genetic placement downstream of fat. However, dachs mutations have only mild tissue polarity phenotypes, and only partially suppress the tissue polarity defects of fat mutants. Our results implicate Dachs as a crucial downstream component of a Fat signaling pathway that influences growth, affinity and gene expression during development.

Amino Acid Sequence↗
PubMed2006

Prdm1 acts downstream of a sequential RA, Wnt and Fgf signaling cascade during zebrafish forelimb induction.

Vertebrate limb induction is triggered in the lateral plate mesoderm (LPM) by a cascade of signaling events originating in the axial mesoderm. While it is known that Fgf, Wnt and retinoic acid (RA) signals are involved in this cascade, their precise regulatory hierarchy has not been determined in any species. tbx5 is the earliest gene expressed in the limb bud mesenchyme. Recently, another transcription factor, Prdm1, has been shown to be crucial for zebrafish forelimb development. Here, we show that Prdm1 is downstream of RA, Wnt2b and Tbx5 activity. We find that RA activity, but not Fgf signaling, is necessary for wnt2b expression. Fgf signaling is required for prdm1 expression in the fin bud, but is not necessary for the initiation of tbx5 expression. We propose a model in which RA signaling from the somitic mesoderm leads to activation of wnt2b expression in the intermediate mesoderm, which then signals to the LPM to trigger tbx5 expression. tbx5 is required for Fgf signaling in the limb bud leading to activation of prdm1 expression, which in turn is required for downstream activation of fgf10 expression.

Animals↗
PubMed1997

CARP, a cardiac ankyrin repeat protein, is downstream in the Nkx2-5 homeobox gene pathway.

To identify the molecular pathways that guide cardiac ventricular chamber specification, maturation and morphogenesis, we have sought to characterize factors that regulate the expression of the ventricular myosin light chain-2 gene, one of the earliest markers of ventricular regionalization during mammalian cardiogenesis. Previously, our laboratory identified a 28 bp HF-la/MEF-2 element in the MLC-2v promoter region, which confers cardiac ventricular chamber-specific gene expression during murine cardiogenesis, and showed that the ubiquitous transcription factor YB-1 binds to the HF-la site in conjunction with a co-factor. In a search for interacting co-factors, a nuclear ankyrin-like repeat protein CARP (cardiac ankyrin repeat protein) was isolated from a rat neonatal heart cDNA library by yeast two-hybrid screening, using YB-1 as the bait. Co-immunoprecipitation and GST-CARP pulldown studies reveal that CARP forms a physical complex with YB-1 in cardiac myocytes and immunostaining shows that endogenous CARP is localized in the cardiac myocyte nucleus. Co-transfection assays indicate that CARP can negatively regulate an HF-1-TK minimal promoter in an HF-1 sequence-dependent manner in cardiac myocytes, and CARP displays a transcriptional inhibitory activity when fused to a GAL4 DNA-binding domain in both cardiac and noncardiac cell context. Northern analysis revealed that carp mRNA is highly enriched in the adult heart, with only trace levels in skeletal muscle. During murine embryogenesis, endogenous carp expression was first clearly detected as early as E8.5 specifically in heart and is regulated temporally and spatially in the myocardium. Nkx2-5, the murine homologue of Drosophila gene tinman was previously shown to be required for heart tube looping morphogenesis and ventricular chamber-specific myosin light chain-2 expression during mammalian heart development. In Nkx2-5(-/-)embryos, carp expression was found to be significantly and selectively reduced as assessed by both whole-mount in situ hybridizations and RNase protection assays, suggesting that carp is downstream of the homeobox gene Nkx2-5 in the cardiac regulatory network. Co-transfection assays using a dominant negative mutant Nkx2-5 construct with CARP promoter-luciferase reporter constructs in cardiac myocytes confirms that Nkx2-5 either directly or indirectly regulates carp at the transcriptional level. Finally, a carp promoter-lacZ transgene, which displays cardiac-specific expression in wild-type and Nkx2-5(+/-) background, was also significantly reduced in Nkx2-5(-/-) embryos, indicating that Nkx2-5 either directly or indirectly regulates carp promoter activity during in vivo cardiogenesis as well as in cultured cardiac myocytes. Thus, CARP is a YB-1 associated factor and represents the first identified cardiac-restricted downstream regulatory gene in the homeobox gene Nkx2-5 pathway and may serve as a negative regulator of HF-1-dependent pathways for ventricular muscle gene expression.

Amino Acid Sequence↗
PubMed1998

Xenopus Smad8 acts downstream of BMP-4 to modulate its activity during vertebrate embryonic patterning.

Bone morphogenetic proteins (BMPs) participate in the development of nearly all organs and tissues. BMP signaling is mediated by specific Smad proteins, Smad1 and/or Smad5, which undergo serine phosphorylation in response to BMP-receptor activation and are then translocated to the nucleus where they modulate transcription of target genes. We have identified a distantly related member of the Xenopus Smad family, Smad8, which lacks the C-terminal SSXS phosphorylation motif present in other Smads, and which appears to function in the BMP signaling pathway. During embryonic development, the spatial pattern of expression of Smad8 mirrors that of BMP-4. We show that an intact BMP signaling pathway is required for its expression. Overexpression of Smad8 in Xenopus embryos phenocopies the effect of blocking BMP-4 signaling, leading to induction of a secondary axis on the ventral side of intact embryos and to direct neural induction in ectodermal explants. Furthermore, Smad8 can block BMP-4-mediated induction of ventral mesoderm-specific gene expression in ectodermal explants. Overexpression of Smad8 within dorsal cells, however, causes patterning defects that are distinct from those reported in BMP-4-deficient embryos, suggesting that Smad8 may interact with additional signaling pathways. Indeed, overexpression of Smad8 blocks expression of Xbra in whole animals, and partially blocks activin signaling in animal caps. In addition, Smad8 inhibits involution of mesodermal cells during gastrulation, a phenotype that is not observed following blockade of activin or BMPs in Xenopus. Together, these results are consistent with the hypothesis that Smad8 participates in a negative feedback loop in which BMP signaling induces the expression of Smad8, which then functions to negatively modulate the amplitude or duration of signaling downstream of BMPs and, possibly, downstream of other transforming growth factor-beta (TGF-beta) family ligands.

Activins↗
PubMed2000

Sloppy paired acts as the downstream target of wingless in the Drosophila CNS and interaction between sloppy paired and gooseberry inhibits sloppy paired during neurogenesis.

Wingless (Wg) and other Wnt proteins play a crucial role in a number of developmental decisions in a variety of organisms. In the ventral nerve cord of the Drosophila embryo, Wg is non-autonomously required for the formation and specification of a neuronal precursor cell, NB4-2. NB4-2 gives rise to a well-studied neuronal lineage, the RP2/sib lineage. While the various components of the Wg-signaling pathway are also required for generating NB4-2, the target gene(s) of this pathway in the signal-receiving cell is not known. In this paper, we show that sloppy paired 1 and sloppy paired 2 function as the downstream targets of the Wg signaling to generate the NB4-2 cell. Thus, while the loss-of-function mutations in wg and slp have the same NB4-2 formation and specification defects, these defects in wg mutants can be rescued by expressing slp genes from a heterologous promoter. That slp genes function downstream of the Wg signaling is also indicated by the result that expression of slp genes is lost from the neuroectoderm in wg mutants and that ectopic expression of wg induces ectopic expression of slp. Finally, previous results show that Gooseberry (Gsb) prevents Wg from specifying NB4-2 identity to the wg-expressing NB5-3. In this paper, we also show that gsb interacts with slp and prevents Slp from specifying NB4-2 identity. Overexpression of slp overcomes this antagonistic interaction and respecifies NB5-3 as NB4-2. This respecification, however, can be suppressed by a simultaneous overexpression of gsb at high levels. This mechanism appears to be responsible for specifying NB5-3 identity to a row 5 neuroblast and preventing Wg from specifying NB4-2 identity to that cell.

Animals↗
PubMed2001

Early embryonic expression of a LIM-homeobox gene Cs-lhx3 is downstream of beta-catenin and responsible for the endoderm differentiation in Ciona savignyi embryos.

In early Ciona embryos, nuclear accumulation of beta-catenin is most probably the first step of endodermal cell specification. If beta-catenin is mis- and/or overexpressed, presumptive notochord cells and epidermal cells change their fates into endodermal cells, whereas if beta-catenin nuclear localization is downregulated by the overexpression of cadherin, the endoderm differentiation is suppressed, accompanied with the differentiation of extra epidermal cells ( Imai, K., Takada, N., Satoh, N. and Satou, Y. (2000) Development 127, 3009-3020). Subtractive hybridization screens of mRNAs between beta-catenin overexpressed embryos and cadherin overexpressed embryos were conducted to identify potential beta-catenin target genes that are responsible for endoderm differentiation in Ciona savignyi embryos. We found that a LIM-homeobox gene (Cs-lhx3), an otx homolog (Cs-otx) and an NK-2 class gene (Cs-ttf1) were among beta-catenin downstream genes. In situ hybridization signals for early zygotic expression of Cs-lhx3 were evident only in the presumptive endodermal cells as early as the 32-cell stage, those of Cs-otx in the mesoendodermal cells at the 32-cell stage and those of Cs-ttf1 in the endodermal cells at the 64-cell stage. Later, Cs-lhx3 was expressed again in a set of neuronal cells in the tailbud embryo, while Cs-otx was expressed in the anterior nervous system of the embryo. Expression of all three genes was upregulated in beta-catenin overexpressed embryos and downregulated in cadherin overexpressed embryos. Injection of morpholino oligonucleotides against Cs-otx did not affect the embryonic endoderm differentiation, although the formation of the central nervous system was suppressed. Injection of Cs-ttf1 morpholino oligonucleotides also failed to suppress the endoderm differentiation, although injection of its synthetic mRNAs resulted in ectopic development of endoderm differentiation marker alkaline phosphatase. By contrast, injection of Cs-lhx3 morpholino oligo suppressed the endodermal cell differentiation and this suppression was rescued by injection of Cs-lhx3 mRNA into eggs. In addition, although injection of delE-Ci-cadherin mRNA into eggs resulted in the suppression of alkaline phosphatase development, injection of delE-Ci-cadherin mRNA with Cs-lhx3 mRNA rescued the alkaline phosphatase development. These results strongly suggest that a LIM-homeobox gene Cs-lhx3 is one of the beta-catenin downstream genes and that its early expression in embryonic endodermal cells is responsible for their differentiation.

Amino Acid Sequence↗
PubMed2005

A novel Sry-downstream cellular event which preserves the readily available energy source of glycogen in mouse sex differentiation.

Sry is transiently activated in pre-Sertoli cells of the gonadal ridge to initiate testis differentiation in mice. In pre-Sertoli cells, however, the cellular events induced immediately after the onset of Sry expression remain largely unknown. Here we show that testis-specific glycogen accumulation in pre-Sertoli cells is one of the earliest cellular events downstream of Sry action. In developing XY gonads, glycogen accumulation starts to occur in pre-Sertoli cells from around 11.15 dpc (tail somite 14 stage) in a center-to-pole pattern similar to the initial Sry expression profile. Glycogen accumulation was also found in XX male gonads of Sry-transgenic embryos, but not in XX female gonads of wildtype embryos at any developmental stage. In vitro analyses using various culture conditions suggest that testis-specific glycogen deposition is a tissue-autonomous event that can be induced even in serum-free conditions and in a culture of gonadal explants without adjacent mesonephros. Moreover, glycogen accumulation in pre-Sertoli cells was significantly inhibited in vitro by the PI3K inhibitor LY294002, but not by the MEK inhibitor PD98059. Active phospho-AKT (PI3K effector) showed a high degree of accumulation in gonadal somatic cells of genital ridges in a testis-specific manner, both in vitro and in vivo. Therefore, these findings suggest that immediately after the onset of Sry expression, activation of the PI3K-AKT pathway promotes testis-specific glycogen storage in pre-Sertoli cells. To the best of our knowledge, this is a novel Sry-downstream cellular event which preserves this readily available energy source in Sertoli cells for testis-specific morphogenesis and hormone production.

Animals↗
PubMed2006

Identification of Jmjd1a as a STAT3 downstream gene in mES cells.

Mouse embryonic stem (mES) cells can be maintained in undifferentiated state in the presence of a cytokine, leukemia inhibitory factor (LIF). Many investigators found that STAT3 activation is important for the maintenance of pluripotency by LIF. However, the downstream pathways of STAT3 activation are still unknown. To look for STAT3-downstream target genes, we performed DD-RT PCR in the presence or absence of LIF. Through further confirmation, we finally selected 8 genes whose expressions were significantly dependent upon the presence of LIF. Among them, Jmjd1a was down-regulated after LIF withdrawal, and it was selected for further investigation. Its expression started to decrease 1 day after the removal of LIF, and disappeared on day 3. It was also shown that STAT3 could bind to the promoter region of Jmjd1a gene. These data demonstrate that Jmjd1a might be a critical signaling molecule underlying the maintenance of pluripotency in mES cells.

Animals↗
PubMed2004

Hypergravity induces phosphorylation of p53 at serine 15, but not an expression of p53-downstream genes.

We investigated the p53 signaling pathway induced by hypergravity in the human glioblastoma cell line A172. Hypergravity (20 x g) induced the accumulation of p53 and the phosphorylation of p53 at Ser-15. The phosphorylation of p53 with hypergravity was not inhibited by wortmannin, the PI3-kinase inhibitor. This indicated that the p53 signal pathway induced by hypergravity is different from other p53 signal pathways, such as that of the DNA damage signal. Hypergravity did not induce an expression of the genes Waf-1 or Bax, located downstream from p53. We also examined the expression of genes with hypergravity by using a DNA microarray containing oligo DNA from 30,000 human genes. Hypergravity (20 x g, 6 h) did induce the expression of some genes concerned with the cell signaling pathway and cytoskeleton of the cell, but not any of the p53-downstream genes. DNA microarray revealed the induction of many genes to enable the cells to adapt to the hypergravity environment.

Amino Acid Sequence↗
PubMed2005

CCR1 acts downstream of NFAT2 in osteoclastogenesis and enhances cell migration.

UNLABELLED: We found that a chemokine receptor gene, CCR1, acts downstream of NFAT2 in RANKL-stimulated RAW264 and bone marrow cells. The upstream regulatory region of CCR1 showed RANKL-dependent and CsA-suppressible promoter activity. Downregulation of the expression and function of CCR1 suppressed cell migration. INTRODUCTION: We previously reported that the expression of NFAT2 induced by RANKL is a key process for progression to multinucleated cells in an in vitro osteoclastogenesis system. Identifying the target genes of NFAT2 would thus be informative about the differentiation process. We focused here on chemokine and chemokine receptor genes that act downstream of NFAT2 in RAW264 cells as well as osteoclast precursors prepared from bone marrow cells. MATERIALS AND METHODS: RAW264 mouse monocyte/macrophage line cells were cultured with or without cyclosporin A (CsA) in the presence of RANKL or glutathione S-transferase (GST). Osteoclast precursors were prepared from bone marrow cells. RANKL-inducible and CsA-suppressible genes were searched for by microarray analysis, and expression was confirmed by quantitative RT-PCR. Promoter activity was measured by luciferase gene reporter assay. Short interfering (si)RNA for CCR1 was introduced in RAW264 cells. Cell migration activity was examined using a Boyden chamber assay. RESULTS AND CONCLUSIONS: We identified the chemokine receptor gene CCR1 as a gene showing significant differential expression profiles in osteoclastogenesis in the presence versus the absence of CsA, an inhibitor of NFAT. This property was unique to CCR1 among the chemokine and chemokine receptor genes examined in both RAW264 and bone marrow cells. The upstream regulatory region was isolated from CCR1, and its RANKL-dependent and CsA-suppressible promoter activity was confirmed. The functional significance of CCR1 was assessed by monitoring the migration of cells in a transwell migration assay, and this activity was abolished when either CsA- or CCR1 siRNA-treated cells were used. Moreover, treatment with a Galpha inhibitor pertussis toxin (PTX) or methiolynated-regulated on activation, normal T cells expressed and secreted (Met-RANTES), an antagonist of CCR1, suppressed multinucleated cell formation in the bone marrow cell system. Together, these results suggest that the CCR1 signaling cascade is under the control of NFAT2 and seems to enhance the migration of differentiating osteoclasts.

Animals↗
PubMed2000

Peroxisome proliferator-activated receptors, coactivators, and downstream targets.

Peroxisomes in liver parenchymal cells proliferate in response to structurally diverse nonmutagenic compounds designated as peroxisome proliferators (PP). Sustained induction of peroxisome proliferation and peroxisomal fatty acid beta-oxidation system in rats and mice leads to the development of liver tumors. Two mechanistic issues are important for consideration: elucidation of the upstream events responsible for the tissue and species specific induction of the characteristic pleiotropic responses by PPs; and delineation of the downstream events associated with peroxisome proliferation, and their role in the development of liver tumors in species that are sensitive to the induction of peroxisome proliferation. The induction of peroxisome proliferation is mediated by PP-activated receptor alpha (PPAR alpha), a member of a group of transcription factors that regulate the expression of genes associated with lipid metabolism and adipocyte differentiation. Three isotypes of this family of nuclear receptors, namely PPAR alpha, PPAR gamma, and PPAR delta (also called beta), have been identified as products of separate genes. Although PPAR alpha is responsible for the PP-induced pleiotropic responses, PPAR gamma seems to be involved in adipogenesis and differentiation, but the events associated with PPAR gamma do not directly involve peroxisomes and peroxisome proliferation. PPARs heterodimerize with 9-cis retinoic acid receptor (RXR), and bind to PP response element(s) (PPREs) on the target gene promoter to initiate inducible transcriptional activity. Tissue and species responses to PPs depend on pharmacokinetics, relative abundance of PPAR isotypes, nature of PPRE in the upstream regions of target genes, the extent of competition or cross-talk among nuclear transcription factors for PPAR heterodimerization partner retinoid X receptor and the modulating role of coactivators and corepressors on ligand-dependent transcription of PPARs. Using PPAR as bait in the yeast two-hybrid system, the authors recently cloned mouse steroid receptor coactivator-1 (SRC-1) and PPAR-binding protein (PBP), and identified them as PPAR coactivators. Both SRC-1 and PBP contain LXXLL signature motifs, considered necessary and sufficient for the binding of coactivators to nuclear receptors. A multifaceted approach, which includes the identification of additional coactivators that may be responsible for cell specific transcriptional activation of PPAR-mediated target genes, and generation of genetically modified animals (transgenic and gene disrupted), will be necessary to gain more insight into the upstream and downstream targets responsible for the induction of early and delayed PP-induced pleiotropic responses. In this context, it is important to note that mice deficient in fatty acyl-CoA oxidase, the first and rate-limiting enzyme of the peroxisomal beta-oxidation system, revealed that this enzyme is indispensable for the physiological regulation of PPAR alpha, and the absence of this enzyme leads to sustained transcriptional activation of genes regulated by this receptor.

Animals↗
PubMed2004

Day-night changes in downstream regulatory element antagonist modulator/potassium channel interacting protein activity contribute to circadian gene expression in pineal gland.

The molecular mechanisms controlling the oscillatory synthesis of melatonin in rat pineal gland involve the rhythmic expression of several genes including arylalkylamine N-acetyltransferase (AA-NAT), inducible cAMP early repressor (ICER), and Fos-related antigen-2 (fra-2). Here we show that the calcium sensors downstream regulatory element antagonist modulator/potassium channel interacting protein (DREAM/KChIP)-3 and KChIP-1, -2 and -4 bind to downstream regulatory element (DRE) sites located in the regulatory regions of these genes and repress basal and induced transcription from ICER, fra-2 or AA-NAT promoters. Importantly, we demonstrate that the endogenous binding activity to DRE sites shows day-night oscillations in rat pineal gland and retina but not in the cerebellum. The peak of DRE binding activity occurs during the day period of the circadian cycle, coinciding with the lowest levels of fra-2, ICER, and AA-NAT transcripts. We show that a rapid clearance of DRE binding activity during the entry in the night period is related to changes at the posttranscriptional level of DREAM/KChIP. The circadian pattern of DREAM/KChIP activity is maintained under constant darkness, indicating that an endogenous clock controls DREAM/KChIP function. Our data suggest involvement of the family of DREAM repressors in the regulation of rhythmically expressed genes engaged in circadian rhythms.

Animals↗
PubMed2005

Downstream regulatory element antagonist modulator regulates Ca2+ homeostasis and viability in cerebellar neurons.

The Na+/Ca2+ exchangers NCX1, NCX2, and NCX3 are vital for the control of cellular Ca2+ homeostasis. Here, we show that a doublet of downstream regulatory element sites in the promoter of the NCX3 gene mediates transcriptional repression of NCX3 by the Ca2+-modulated transcriptional repressor downstream regulatory element antagonist modulator (DREAM). Overexpression of a DREAM EF-hand mutant insensitive to Ca2+ (EFmDREAM) in hippocampus and cerebellum of transgenic mice significantly reduced NCX3 mRNA and protein levels without modifying NCX1 and NCX2 expression. Cerebellar granules from EFmDREAM transgenic mice showed increased levels of cytosolic Ca2+ and were more vulnerable to increased Ca2+ influx after partial opening of voltage-gated plasma membrane Ca2+ channels induced by increasing K+ in the culture medium but survived better in the conditions of reduced Ca2+ influx prevailing in low extracellular K+. Overexpression of NCX3 in EFmDREAM transgenic granules using a lentiviral vector restored the normal survival response to high K+ observed in wild-type granules. Thus, the downregulation of the regulator of Ca2+ homeostasis NCX3 by Ca2+-regulated DREAM is a striking example of the autoregulatory property of the Ca2+ signal in neurons.

Amino Acid Motifs↗
PubMed2000

UVB-induced epidermal growth factor receptor phosphorylation is critical for downstream signaling and keratinocyte survival.

We have recently shown that UVB radiation activates epidermal growth factor receptor (EGFR)/extracellular regulated kinase 1 and 2 (ERK1/2) and p38 signaling pathways in keratinocytes. However, the functional relevance of these processes for downstream signaling and cell survival remains to be determined. The specific EGFR inhibitor PD153035 markedly decreased UVB-induced phosphorylation of EGFR, ERK1/2 and shc, whereas p38 activation was unaffected. PD153035 pretreatment followed by UVB reduced clonogenic potential and enhanced peroxide production, apoptosis and cell death. Our data suggest that ligand-independent phosphorylation of EGFR and likely dependent downstream signaling pathways regulate cellular defense mechanisms important for cell survival following oxidative stress.

Cell Survival↗