Induction Of Immediate Early Genes Research Articles

Neuromodulatory effect of Gαs- or Gαq-coupled G-protein-coupled receptor on NMDA receptor selectively activates the NMDA receptor/Ca2+/calcineurin/cAMP response element-binding protein-regulated transcriptional coactivator 1 pathway to effectively induce brain-derived neurotrophic factor expression in neurons.

Although coordinated molecular signaling through excitatory and modulatory neurotransmissions is critical for the induction of immediate early genes (IEGs), which lead to effective changes in synaptic plasticity, the intracellular mechanisms responsible remain obscure. Here we measured the expression of IEGs and used bioluminescence imaging to visualize the expression of Bdnf when GPCRs, major neuromodulator receptors, were stimulated. Stimulation of pituitary adenylate cyclase-activating polypeptide (PACAP)-specific receptor (PAC1), a Gαs/q-protein-coupled GPCR, with PACAP selectively activated the calcineurin (CN) pathway that is controlled by calcium signals evoked via NMDAR. This signaling pathway then induced the expression of Bdnf and CN-dependent IEGs through the nuclear translocation of CREB-regulated transcriptional coactivator 1 (CRTC1). Intracerebroventricular injection of PACAP and intraperitoneal administration of MK801 in mice demonstrated that functional interactions between PAC1 and NMDAR induced the expression of Bdnf in the brain. Coactivation of NMDAR and PAC1 synergistically induced the expression of Bdnf attributable to selective activation of the CN pathway. This CN pathway-controlled expression of Bdnf was also induced by stimulating other Gαs- or Gαq-coupled GPCRs, such as dopamine D1, adrenaline β, CRF, and neurotensin receptors, either with their cognate agonists or by direct stimulation of the protein kinase A (PKA)/PKC pathway with chemical activators. Thus, the GPCR-induced expression of IEGs in coordination with NMDAR might occur via the selective activation of the CN/CRTC1/CREB pathway under simultaneous excitatory and modulatory synaptic transmissions in neurons if either the Gαs/adenylate cyclase/PKA or Gαq/PLC/PKC-mediated pathway is activated.

Activity-dependent expression of miR-132 regulates immediate-early gene induction during olfactory learning in the greater short-nosed fruit bat, Cynopterus sphinx

The activity-dependent expression of immediate-early genes (IEGs) and microRNA (miR)-132 has been implicated in synaptic plasticity and the formation of long-term memory (LTM). In the present study, we show that olfactory training induces the expression of IEGs (EGR-1, C-fos, C-jun) and miR-132 at similar time scale in olfactory bulb (OB) of Cynopterus sphinx. We examined the role of miR-132 in the OB using antisense oligodeoxynucleotide (AS-ODN) and demonstrated that a local infusion of AS-ODN in the OB 2h prior to training impaired olfactory memory formation in C. sphinx. However, the infusion of AS-ODN post-training did not cause a deficit in memory formation. Furthermore, the inhibition of miR-132 reduced the olfactory training-induced expression of IEGs and post synaptic density protein-95 (PSD-95) in the OB. Additionally, we show that miR-132 regulates the activation of calcium/calmodulin-dependent protein kinase-II (CaMKII) and cAMP response element binding protein (CREB), possibly through miR-148a. These data suggest that olfactory training induces the expression of miR-132 and IEGs, which in turn activates post-synaptic proteins that regulate olfactory memory formation.

Blocking miRNA Biogenesis in Adult Forebrain Neurons Enhances Seizure Susceptibility, Fear Memory, and Food Intake by Increasing Neuronal Responsiveness.

The RNase Dicer is essential for the maturation of most microRNAs, a molecular system that plays an essential role in fine-tuning gene expression. To gain molecular insight into the role of Dicer and the microRNA system in brain function, we conducted 2 complementary RNA-seq screens in the hippocampus of inducible forebrain-restricted Dicer1 mutants aimed at identifying the microRNAs primarily affected by Dicer loss and their targets, respectively. Functional genomics analyses predicted the main biological processes and phenotypes associated with impaired microRNA maturation, including categories related to microRNA biology, signal transduction, seizures, and synaptic transmission and plasticity. Consistent with these predictions, we found that, soon after recombination, Dicer-deficient mice exhibited an exaggerated seizure response, enhanced induction of immediate early genes in response to different stimuli, stronger and more stable fear memory, hyperphagia, and increased excitability of CA1 pyramidal neurons. In the long term, we also observed slow and progressive excitotoxic neurodegeneration. Overall, our results indicate that interfering with microRNA biogenesis causes an increase in neuronal responsiveness and disrupts homeostatic mechanisms that protect the neuron against overactivation, which may explain both the initial and late phenotypes associated with the loss of Dicer in excitatory neurons.

Nuclear factor kappa B-dependent Zif268 expression in hippocampus is required for recognition memory in mice

Long-term memory formation requires gene expression after acquisition of new information. The first step in the regulation of gene expression is the participation of transcription factors (TFs) such as nuclear factor kappa B (NF-кB), which are present before the neuronal activity induced by training. It was proposed that the activation of these types of TFs allows a second step in gene regulation by induction of immediate-early genes (IEGs) whose protein products are, in turn, TFs. Between these IEGs, zif268 has been found to play a critical role in long-term memory formation and reprocessing after retrieval. Here we found in mice hippocampus that, on one hand, NF-кB was activated 45min after training in a novel object recognition (NOR) task and that inhibiting NF-кB immediately after training by intrahippocampal administration of NF-кB Decoy DNA impaired NOR memory consolidation. On the other hand, Zif268 protein expression was induced 45min after NOR training and the administration of DNA antisense to its mRNA post-training impaired recognition memory. Finally, we found that the inhibition of NF-кB by NF-кB Decoy DNA reduced significantly the training-induced Zif268 increment, indicating that NF-кB is involved in the regulation of Zif268 expression. Thus, the present results support the involvement of NF-кB activity-dependent Zif268 expression in the hippocampus during recognition memory consolidation.

An Integrated Approach for the Identification of HNF4α-Centered Transcriptional Regulatory Networks During Early Liver Regeneration

Background/Aims: Hepatocyte nuclear factor-4α (HNF4α), the liver enriched transcription factor (TF), is one of the major regulators of hepatocyte differentiation and proliferation. However, how HNF4α participate in liver regeneration after partial hepatectomy (PH) remains largely unknown. In order to identify the HNF4α-centered regulatory network, we applied an integrated analytic strategy, in which, TF array, mRNA microarray, bioinformatic analysis and ChIP-on-chip assays were integrated. Methods/Results: The TF signatures from MOUSE OATFA (TF-array) platform revealed that the activity of HNF4α was significantly reduced and 17 other TFs showed increased activity at 4 h post PH. Then the ChIP-on-chip analysis on HNF4α were combined with mRNA expression profiling to select the possible HNF4α target genes during early liver regeneration, which were then sub-grouped according to their signaling pathways. More specifically, the HNF4α target genes with the gene ontology (GO) terms of cytokine-cytokine receptor, Jak-STAT, MAPK, toll-like receptor and insulin signaling pathways were further analyzed with an advanced bioinformatics tool named oPOSSUM to identify TF binding sites occupancy and predict the co-regulatory relationship between TFs and targets. Furthermore, we identified that repressed HNF4α during the early phase of liver regeneration may contribute cooperatively to the induction of immediate early genes, such as, c-fos, c-jun and stat3. Conclusion: our data indicate that HNF4α may play an inhibitory role on the induction of specific promitogenic genes and liver regeneration initiation. The integrated approach of mRNA/OATFA/ChIP-DSL/oPOSSUM analysis may help us better characterize the target genes and co-regulatory network of HNF4α during the early stage of liver regeneration.

Cocaine induces ubiquitination of Egr-1 in the rat dorsal striatum.

Early growth response (Egr) is a member of the zinc finger family of transcription factors that reflects neuronal activity induced by various stimuli. Acute cocaine administration elicits rapid and transient induction of several immediate early genes in brain neurons. However, the mechanism regulating the degradation of the Egr-1 protein is not clearly understood. In this study, rats were injected with cocaine and the relationships among locomotor activity, Egr-1 protein level, phosphorylation of upstream kinase extracellular regulated kinase (ERK)1/2, Egr-1 mRNA expression, and ubiquitination of the Egr-1 protein were measured in the dorsal striatum and the frontal cortex. Locomotor activity reached a peak at about 15 min, and phosphorylation of ERK1/2 and Egr-1 mRNA level also increased at that time. However, the Egr-1 protein level decreased initially in the dorsal striatum, probably due to ubiquitination-mediated degradation. When locomotor activity decreased substantially at 30 min, the phosphorylation of ERKs and expression levels of Egr-1 mRNA and protein reached their peak levels and the protein level subsequently increased. These findings indicate that immediate early gene protein levels would not be a reliable indicator of increased regional activity in the brain. Thus, observations spanning multiple time periods or the examination of mRNA rather than protein would be recommended in these situations.

Temporal and anatomic patterns of immediate-early gene expression in the forebrain of C57BL/6 and DBA/2 mice after morphine administration

Although morphine was previously reported to produce an instant induction of c-fos in the striatum, our recent studies have demonstrated that the expression of numerous immediate early genes (IEGs) is significantly elevated at delayed time-points (several hours) after morphine administration. To better dissect the time-course of opioid-produced IEG induction, we used in situ hybridization to examine the expression of the IEGs c-fos, zif268 and arc in the mouse forebrain at several time-points after acute morphine injection. To link drug-produced behavioral changes with the activity of specific neuronal complexes, this study was performed comparatively in the C57BL/6 and DBA/2 mouse strains, which differ markedly in their locomotor responses to opioids and opioid reward.Our study demonstrates that morphine produces two episodes of IEG induction, which are separate in time (30min vs. 4–6h) and which have different neuroanatomic distribution. At 30min, one or more IEGs were induced in circumscribed subregions of the dorsal striatum (dStr) and of the nucleus accumbens (NAc) shell, as well as in the lateral septum. The observed inter-strain differences in IEG expression at 30min support earlier proposals that activation of the dorsomedial striatum may mediate morphine-elicited locomotor stimulation (both effects were present only in the C57BL/6 strain). In contrast, NAc shell activation does not appear to be linked to morphine-elicited changes in locomotor behavior. The second IEG induction (of arc and of zif268) was more widespread, involving most of the dStr and the cortex. The second IEG induction peaked earlier in the DBA/2 mice than in the C57BL/6 mice (4h compared with 6h) and displayed no apparent relation to locomotor behavior. This delayed episode of IEG activation, which has largely been overlooked thus far, may contribute to the development of long-term effects of opioids such as tolerance, dependence and/or addiction.

Abstract 5112: Histone deacetylase and proteasome inhibitors synergistically induce apoptosis in colon cancer, multiple myeloma and CTCL cells through induction of the immediate early genes ATF3 and JUN

Abstract Background/Aim: Histone deacetylase inhibitors (HDACi) are approved for the treatment of cutaneous T-cell lymphoma. We have previously demonstrated that HDACi-mediated apoptosis is linked to the induction of a defined transcriptional response involving up-regulation of the immediate-early (IE) genes FOS, JUN, ATF3, EGR1 and EGR3, in cell lines derived from multiple tumour types. To identify other drugs which induce a similar transcriptional response we compared the HDACi-induced transcriptional response with that induced by >1000 bioactive molecules using the Broad Institute's Connectivity Map database. The proteasome inhibitor, MG-262, was identified as inducing the most comparable transcriptional response to HDACi. Notably, combination treatment with HDAC and proteasome inhibitors has been shown to synergistically induce apoptosis in vitro, and a phase III trial of this combination demonstrated activity in patients multiple myeloma. The aim of this study was to determine whether these effects are mediated through the additive induction of IE genes. Methods: The effect of the HDACi SAHA and the clinically approved proteasome inhibitor Bortezomib, alone, and in combination, on apoptosis induction was determined in colorectal, multiple myeloma and CTCL cell lines PI staining and FACS analysis. Quantitative RT-PCR was performed to determine gene expression changes upon drug treatment. MAPK pathway activation and histone hyper-acetylation was determined by western blot analysis. Results: Single agent treatment of multiple cancer cells with SAHA or Bortezomib induced expression of the IE genes FOS, JUN and ATF3. In both cases IE gene induction was sustained over 24h. Proteasome inhibitor-induced IE gene expression and apoptosis was selectively dependent on activation of the JNK and p38 stress response pathways, while HDACi-mediated effects were selectively dependent upon the Sp1 and Sp3 transcription factors, indicating these agents induce IE gene expression and apoptosis via independent mechanisms. Co-treatment with Bortezomib and SAHA resulted in synergistic induction of IE gene expression and apoptosis in cell lines derived from multiple tumour types. Importantly, apoptosis induction by the combination was partially inhibited by siRNA-mediated downregulation of two IE genes, ATF3 and JUN. Conclusions: This study provides insight into the mechanistic basis by which combination treatment with HDAC and proteasome inhibitors synergistically induces apoptosis in tumour cells. Citation Format: Janson WT Tse, Anderly C. Chueh, Ian Y. Luk, Fiona Chionh, Yvonne Yeung, Georgia A. Corner, Dominic CH Ng, Hoanh Tran, Amardeep S. Dhillon, John M. Mariadason. Histone deacetylase and proteasome inhibitors synergistically induce apoptosis in colon cancer, multiple myeloma and CTCL cells through induction of the immediate early genes ATF3 and JUN. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5112. doi:10.1158/1538-7445.AM2014-5112

Enhancer RNA Facilitates NELF Release from Immediate Early Genes

Enhancer RNAs (eRNAs) are a class of long noncoding RNAs (lncRNA) expressed from active enhancers, whose function and action mechanism are yet to be firmly established. Here we show that eRNAs facilitate the transition of paused RNA polymerase II (RNAPII) into productive elongation by acting as a decoy for the negative elongation factor (NELF) complex upon induction of immediate early genes (IEGs) in neurons. eRNAs are synthesized prior to the culmination of target gene transcription and interact with the NELF complex. Knockdown of eRNAs expressed at neuronal enhancers impairs transient release of NELF from the specific target promoters during transcriptional activation, coinciding with a decrease in target mRNA induction. The enhancer-promoter interaction was unaffected by eRNA knockdown. Instead, chromatin looping might enable eRNAs to act locally at a specific promoter. Our findings highlight the spatiotemporally regulated action mechanism of eRNAs during early transcriptional elongation.

Novel aspects of glucocorticoid actions.

Normal hypothalamic-pituitary-adrenal (HPA) axis activity leading to the rhythmic and episodic release of adrenal glucocorticoids (GCs) is essential for body homeostasis and survival during stress. Acting through specific intracellular receptors in the brain and periphery, GCs regulate behaviour, as well as metabolic, cardiovascular, immune and neuroendocrine activities. By contrast to chronic elevated levels, circadian and acute stress-induced increases in GCs are necessary for hippocampal neuronal survival and memory acquisition and consolidation, as a result of the inhibition of apoptosis, the facilitation of glutamatergic neurotransmission and the formation of excitatory synapses, and the induction of immediate early genes and dendritic spine formation. In addition to metabolic actions leading to increased energy availability, GCs have profound effects on feeding behaviour, mainly via the modulation of orexigenic and anorixegenic neuropeptides. Evidence is also emerging that, in addition to the recognised immune suppressive actions of GCs by counteracting adrenergic pro-inflammatory actions, circadian elevations have priming effects in the immune system, potentiating acute defensive responses. In addition, negative-feedback by GCs involves multiple mechanisms leading to limited HPA axis activation and prevention of the deleterious effects of excessive GC production. Adequate GC secretion to meet body demands is tightly regulated by a complex neural circuitry controlling hypothalamic corticotrophin-releasing hormone (CRH) and vasopressin secretion, which are the main regulators of pituitary adrenocorticotrophic hormone (ACTH). Rapid feedback mechanisms, likely involving nongenomic actions of GCs, mediate the immediate inhibition of hypothalamic CRH and ACTH secretion, whereas intermediate and delayed mechanisms mediated by genomic actions involve the modulation of limbic circuitry and peripheral metabolic messengers. Consistent with their key adaptive roles, HPA axis components are evolutionarily conserved, being present in the earliest vertebrates. An understanding of these basic mechanisms may lead to novel approaches for the development of diagnostic and therapeutic tools for disorders related to stress and alterations of GC secretion.

Manganese-enhanced magnetic resonance imaging reveals increased DOI-induced brain activity in a mouse model of schizophrenia

Maternal infection during pregnancy increases the risk for schizophrenia in offspring. In rodent models, maternal immune activation (MIA) yields offspring with schizophrenia-like behaviors. None of these behaviors are, however, specific to schizophrenia. The presence of hallucinations is a key diagnostic symptom of schizophrenia. In mice, this symptom can be defined as brain activation in the absence of external stimuli, which can be mimicked by administration of hallucinogens. We find that, compared with controls, adult MIA offspring display an increased stereotypical behavioral response to the hallucinogen 2,5-dimethoxy-4-iodoamphetamine (DOI), an agonist for serotonin receptor 2A (5-HT2AR). This may be explained by increased levels of 5-HT2AR and downstream signaling molecules in unstimulated MIA prefrontal cortex (PFC). Using manganese-enhanced magnetic resonance imaging to identify neuronal activation elicited by DOI administration, we find that, compared with controls, MIA offspring exhibit a greater manganese (Mn(2+)) accumulation in several brain areas, including the PFC, thalamus, and striatum. The parafascicular thalamic nucleus, which plays the role in the pathogenesis of hallucinations, is activated by DOI in MIA offspring only. Additionally, compared with controls, MIA offspring demonstrate higher DOI-induced expression of early growth response protein 1, cyclooxygenase-2, and brain-derived neurotrophic factor in the PFC. Chronic treatment with the 5-HT2AR antagonist ketanserin reduces DOI-induced head twitching in MIA offspring. Thus, the MIA mouse model can be successfully used to investigate activity induced by DOI in awake, behaving mice. Moreover, manganese-enhanced magnetic resonance imaging is a useful, noninvasive method for accurately measuring this type of activity.

Ropinirole regulates emotionality and neuronal activity markers in the limbic forebrain.

Restless legs syndrome (RLS) and Parkinson's disease (PD) are movement disorders usually accompanied by emotional and cognitive deficits. Although D3/D2 receptor agonists are effective against motor and non-motor deficits in RLS and PD, the exact behavioral and neurochemical effects of these drugs are not clearly defined. This study aimed to evaluate the effects of acute ropinirole (0, 0.1, 1 or 10 mg/kg, i.p.), a preferential D3/D2 receptor agonist, on intracranial self-stimulation (ICSS), spontaneous motor activity, anxiety- and depression-like behaviors, spatial reference and working memory in rats as well as on certain markers of neuronal activity, i.e. induction of immediate early genes, such as c-fos and arc, and crucial phosphorylations on GluA1 subunit of α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and NA1, NA2A and NA2B subunits of N-methyl-D-aspartate (NMDA) receptors. Ropinirole decreased ICSS thresholds and induced anxiolytic- and antidepressive-like effects without affecting motor activity or spatial memory. The effects on emotionality were associated with a decrease in p-Ser897-NA1 and an increase in p-Tyr1472-NA2B in the ventral striatum as well as an increased induction of c-fos messenger RNA (mRNA) in the prefrontal cortex (PFC) and decreased expression of arc mRNA in the striatum and the shell of the nucleus accumbens. Our data indicate that ropinirole significantly affects emotionality at doses (1-10 mg/kg, i.p.) that exert no robust effects on locomotion or cognition. The data reinforce the use of D3/D2 receptor agonists in the treatment of RLS and PD patients characterized by emotional deficits and suggest that altered NMDA-mediated neurotransmission in the limbic forebrain may underlie some of ropinirole's therapeutic actions.

Fibroblast growth factor 15 deficiency impairs liver regeneration in mice

Fibroblast growth factor (FGF) 15 (human homolog, FGF19) is an endocrine FGF highly expressed in the small intestine of mice. Emerging evidence suggests that FGF15 is critical for regulating hepatic functions; however, the role of FGF15 in liver regeneration is unclear. This study assessed whether liver regeneration is altered in FGF15 knockout (KO) mice following 2/3 partial hepatectomy (PHx). The results showed that FGF15 KO mice had marked mortality, with the survival rate influenced by genetic background. Compared with wild-type mice, the KO mice displayed extensive liver necrosis and marked elevation of serum bile acids and bilirubin. Furthermore, hepatocyte proliferation was reduced in the KO mice because of impaired cell cycle progression. After PHx, the KO mice had weaker activation of signaling pathways that are important for liver regeneration, including signal transducer and activator of transcription 3, nuclear factor-κB, and mitogen-activated protein kinase. Examination of the KO mice at early time points after PHx revealed a reduced and/or delayed induction of immediate-early response genes, including growth-control transcription factors that are critical for liver regeneration. In conclusion, the results suggest that FGF15 deficiency severely impairs liver regeneration in mice after PHx. The underlying mechanism is likely the result of disrupted bile acid homeostasis and impaired priming of hepatocyte proliferation.

Abstract P3-01-02: Oxalate microcalcifications induce breast cancer tumors

Abstract One shared characteristic of breast cancer is the appearance of mammographic upon mammography examination. Microcalcifications are routinely used to detect breast cancer in its early stages, which is of key importance due to the possibility that early detection gives for the application of more conservative therapies and for a better patient outcome. Mammary microcalcifications are composed of calcium oxalate or calcium phosphate. Oxalate has been considered as an inert end product of the metabolism. However, its accumulation is thought to be toxic to living tissues because it induces some pathological circumstances. Several results support the hypothesis that Oxalates are a secretion product that is produced by many kinds of cells, including apocrine cells, kidney cells and liver cells, among others. Exposure of renal epithelial cells to oxalate leads to diverse events that include, among others, induction of immediate early genes (IEG) expression, re-initiation of DNA synthesis, cell growth, and up or down-regulation of more than 1000 genes. Not enough research has been carried out directed to investigate the impact the presence of oxalates has within the breast tumor microenvironment. Neither are the interactions between oxalates breast-epithelial cells nor the signal transduction pathways involved in it, well understood. Herein, we have obtained good evidence showing that oxalates excreted from apocrine cells induce alterations in normal breast epithelial cells, and that the exposure of breast epithelial cells to excreted oxalate in a chronic way, sets the stage for transformation from normal to fully developed breast tumors. Oxalate induces DNA synthesis and IEG overexpression in MCF7 and MDAMB231 human breast cancer cells in culture. When these cells were treated with oxalate, the IEG c-Fos and Fra-1 were over-expressed as determined by Western Blot. Additionally, in human breast cancer tissues we found a strict correlation between oxalate concentration and overexpression of c-Fos and Fra-1. Paired adjacent non-tumor tissues linked with the tumor tissues have neither high levels of oxalate nor c-Fos/Fra-1 over-expression. Two groups of female mice (n = 20 each) periodically received an injection of oxalate or of saline solution (controls) into a mammary fatpad during a month. Surprisingly, the mice that were injected with oxalate generated very aggressive tumors. c-Fos and Fra-1 were also found over-expressed in these tumors. Furthermore, the final oxalate concentrations in the mice tumors were analogous to those found in the human breast tumor tissues whereas oxalate was almost undetectable in the non-pathological control tissues. Mice breast tumors were palpable within three months in 18/20 of oxalate treated as compared to the 0/20 control animals. Eight tumors were very aggressive and showed very fast growth rates; in these tumors, it was possible to appreciate high rate of atypical mitosis upon haematoxylin/eosin staining. Five tumors were very invasive and were found multi-localized in all breast areas. These five tumors also showed an atypically high mitotic rate, big pleomorphic nuclei, and macro and multi nucleoli. We expect that if we can control oxalic production or even better, control their action, we will significantly reduce the development of human breast cancers. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P3-01-02.

Inositol polyphosphate multikinase is a coactivator for serum response factor-dependent induction of immediate early genes

Inositol polyphosphate multikinase (IPMK) is a notably pleiotropic protein. It displays both inositol phosphate kinase and phosphatidylinositol kinase catalytic activities. Noncatalytically, IPMK stabilizes the mammalian target of rapamycin complex 1 and acts as a transcriptional coactivator for CREB-binding protein/E1A binding protein p300 and tumor suppressor protein p53. Serum response factor (SRF) is a major transcription factor for a wide range of immediate early genes. We report that IPMK, in a noncatalytic role, is a transcriptional coactivator for SRF mediating the transcription of immediate early genes. Stimulation by serum of many immediate early genes is greatly reduced by IPMK deletion. IPMK stimulates expression of these genes, an influence also displayed by catalytically inactive IPMK. IPMK acts by binding directly to SRF and thereby enhancing interactions of SRF with the serum response element of diverse genes.

Inositol polyphosphate multikinase is a transcriptional coactivator required for immediate early gene induction

Profound induction of immediate early genes (IEGs) by neural activation is a critical determinant for plasticity in the brain, but intervening molecular signals are not well characterized. We demonstrate that inositol polyphosphate multikinase (IPMK) acts noncatalytically as a transcriptional coactivator to mediate induction of numerous IEGs. IEG induction by electroconvulsive stimulation is virtually abolished in the brains of IPMK-deleted mice, which also display deficits in spatial memory. Neural activity stimulates binding of IPMK to the histone acetyltransferase CBP and enhances its recruitment to IEG promoters. Interestingly, IPMK regulation of CBP recruitment and IEG induction does not require its catalytic activities. Dominant-negative constructs, which prevent IPMK-CBP binding, substantially decrease IEG induction. As IPMK is ubiquitously expressed, its epigenetic regulation of IEGs may influence diverse nonneural and neural biologic processes.

Abortive Lytic Reactivation of KSHV in CBF1/CSL Deficient Human B Cell Lines

Since Kaposi's sarcoma associated herpesvirus (KSHV) establishes a persistent infection in human B cells, B cells are a critical compartment for viral pathogenesis. RTA, the replication and transcription activator of KSHV, can either directly bind to DNA or use cellular DNA binding factors including CBF1/CSL as DNA adaptors. In addition, the viral factors LANA1 and vIRF4 are known to bind to CBF1/CSL and modulate RTA activity. To analyze the contribution of CBF1/CSL to reactivation in human B cells, we have successfully infected DG75 and DG75 CBF1/CSL knock-out cell lines with recombinant KSHV.219 and selected for viral maintenance by selective medium. Both lines maintained the virus irrespective of their CBF1/CSL status. Viral reactivation could be initiated in both B cell lines but viral genome replication was attenuated in CBF1/CSL deficient lines, which also failed to produce detectable levels of infectious virus. Induction of immediate early, early and late viral genes was impaired in CBF1/CSL deficient cells at multiple stages of the reactivation process but could be restored to wild-type levels by reintroduction of CBF1/CSL. To identify additional viral RTA target genes, which are directly controlled by CBF1/CSL, we analyzed promoters of a selected subset of viral genes. We show that the induction of the late viral genes ORF29a and ORF65 by RTA is strongly enhanced by CBF1/CSL. Orthologs of ORF29a in other herpesviruses are part of the terminase complex required for viral packaging. ORF65 encodes the small capsid protein essential for capsid shell assembly. Our study demonstrates for the first time that in human B cells viral replication can be initiated in the absence of CBF1/CSL but the reactivation process is severely attenuated at all stages and does not lead to virion production. Thus, CBF1/CSL acts as a global hub which is used by the virus to coordinate the lytic cascade.

ERK2 Suppresses Self-Renewal Capacity of Embryonic Stem Cells, but Is Not Required for Multi-Lineage Commitment

Activation of the FGF-ERK pathway is necessary for naïve mouse embryonic stem (ES) cells to exit self-renewal and commit to early differentiated lineages. Here we show that genetic ablation of Erk2, the predominant ERK isozyme expressed in ES cells, results in hyper-phosphorylation of ERK1, but an overall decrease in total ERK activity as judged by substrate phosphorylation and immediate-early gene (IEG) induction. Normal induction of this subset of canonical ERK targets, as well as p90RSK phosphorylation, was rescued by transgenic expression of either ERK1 or ERK2 indicating a degree of functional redundancy. In contrast to previously published work, Erk2-null ES cells exhibited no detectable defect in lineage specification to any of the three germ layers when induced to differentiate in either embryoid bodies or in defined neural induction conditions. However, under self-renewing conditions Erk2-null ES cells express increased levels of the pluripotency-associated transcripts, Nanog and Tbx3, a decrease in Nanog-GFP heterogeneity, and exhibit enhanced self-renewal in colony forming assays. Transgenic add-back of ERK2 is capable of restoring normal pluripotent gene expression and self-renewal capacity. We show that ERK2 contributes to the destabilization of ES cell self-renewal by reducing expression of pluripotency genes, such as Nanog, but is not specifically required for the early stages of germ layer specification.

STAT3-mediated Coincidence Detection Regulates Noncanonical Immediate Early Gene Induction

Signaling pathways interact with one another to form dynamic networks in which the cellular response to one stimulus may depend on the presence, intensity, timing, or localization of other signals. In rare cases, two stimuli may be simultaneously required for cells to elicit a significant biological output. This phenomenon, generally termed "coincidence detection," requires a downstream signaling node that functions as a Boolean AND gate to restrict biological output from a network unless multiple stimuli are received within a specific window of time. Simultaneous activation of the EGF receptor (EGFR) and a thrombin receptor (protease-activated receptor-1, PAR-1) increases the expression of multiple immediate early genes (IEGs) associated with growth and angiogenesis. Using a bioinformatic comparison of IEG promoter regions, we identified STAT3 as a critical transcription factor for the detection of coincident EGFR/PAR-1 activation. EGFR activation induces classical STAT3 Tyr(705) phosphorylation but also initiates an inhibitory signal through the PI3K-AKT signaling axis that prevents STAT3 Ser(727) phosphorylation. Coincident PAR-1 signaling resolves these conflicting EGF-activated pathways by blocking AKT activation and permitting GSK-3α/β-dependent STAT3 Ser(727) phosphorylation and STAT3-dependent gene expression. Functionally, combinatorial EGFR/PAR-1 signaling suppresses EGF-induced proliferation and thrombin-induced leukocyte adhesion and triggers a STAT3-dependent increase in endothelial cell migration. This study reveals a novel signaling role for STAT3 in which the simultaneous presence of extracellular EGF and thrombin is detected at the level of STAT3 post-translational modifications. Collectively, our results describe a novel regulatory mechanism in which combinatorial EGFR/PAR-1 signaling regulates STAT3-dependent IEG induction and endothelial cell migration.

An integrated understanding of the physiological response to elevated extracellular phosphate

Recent studies have suggested that changes in serum phosphate levels influence pathological states associated with aging such as cancer, bone metabolism, and cardiovascular function, even in individuals with normal renal function. The causes are only beginning to be elucidated but are likely a combination of endocrine, paracrine, autocrine, and cell autonomous effects. We have used an integrated quantitative biology approach, combining transcriptomics and proteomics to define a multi-phase, extracellular phosphate-induced, signaling network in pre-osteoblasts as well as primary human and mouse mesenchymal stromal cells. We identified a rapid mitogenic response stimulated by elevated phosphate that results in the induction of immediate early genes including c-fos. The mechanism of activation requires FGF receptor signaling followed by stimulation of N-Ras and activation of AP-1 and serum response elements. A distinct long-term response also requires FGF receptor signaling and results in N-Ras activation and expression of genes and secretion of proteins involved in matrix regulation, calcification, and angiogenesis. The late response is synergistically enhanced by addition of FGF23 peptide. The intermediate phase results in increased oxidative phosphorylation and ATP production and is necessary for the late response providing a functional link between the phases. Collectively, the results define elevated phosphate, as a mitogen and define specific mechanisms by which phosphate stimulates proliferation and matrix regulation. Our approach provides a comprehensive understanding of the cellular response to elevated extracellular phosphate, functionally connecting temporally coordinated signaling, transcriptional, and metabolic events with changes in long-term cell behavior.