The mouse nac1 gene, encoding a cocaine-regulated bric-a-brac tramtrac broad complex/pox virus and zinc finger protein, is regulated by ap1

Nacc1 Mutation in Mice Models Rare Neurodevelopmental Disorder with Underlying Synaptic Dysfunction

A missense mutation in the transcription repressor Nucleus accumbens-associated 1 (NACC1) gene at c.892C>T (p.Arg298Trp) on chromosome 19 causes severe neurodevelopmental delay ( Schoch et al., 2017). To model this disorder, we engineered the first mouse model with the homologous mutation (Nacc1+/R284W ) and examined mice from E17.5 to 8 months. Both genders had delayed weight gain, epileptiform discharges and altered power spectral distribution in cortical electroencephalogram, behavioral seizures, and marked hindlimb clasping; females displayed thigmotaxis in an open field. In the cortex, NACC1 long isoform, which harbors the mutation, increased from 3 to 6 months, whereas the short isoform, which is not present in humans and lacks aaR284 in mice, rose steadily from postnatal day (P) 7. Nuclear NACC1 immunoreactivity increased in cortical pyramidal neurons and parvalbumin containing interneurons but not in nuclei of astrocytes or oligodendroglia. Glial fibrillary acidic protein staining in astrocytic processes was diminished. RNA-seq of P14 mutant mice cortex revealed over 1,000 differentially expressed genes (DEGs). Glial transcripts were downregulated and synaptic genes upregulated. Top gene ontology terms from upregulated DEGs relate to postsynapse and ion channel function, while downregulated DEGs enriched for terms relating to metabolic function, mitochondria, and ribosomes. Levels of synaptic proteins were changed, but number and length of synaptic contacts were unaltered at 3 months. Homozygosity worsened some phenotypes including postnatal survival, weight gain delay, and increase in nuclear NACC1. This mouse model simulates a rare form of autism and will be indispensable for assessing pathophysiology and targets for therapeutic intervention.

An overview of the co-transcription factor NACC1: Beyond its pro-tumor effects

Nucleus accumbens-associated protein 1 (NACC1) is a member of the broad complex, tramtrack, bric-a-brac/poxvirus and zinc finger (BTB/POZ) protein families, mainly exerting its biological functions as a transcription co-regulator. NACC1 forms homo- or hetero-dimers through the BTB/POZ or BANP, E5R, and NACC1 (BEN) domain with other transcriptional regulators to regulate downstream signals. Recently, the overexpression of NACC1 has been observed in various tumors and is positively associated with tumor progression, high recurrence rate, indicating poor prognosis. NACC1 also regulates biological processes such as embryonic development, stem cell pluripotency, innate immunity, and related diseases. Our review combines recent research to summarize advancements in the structure, biological functions, and relative molecular mechanisms of NACC1. The future development of NACC1 clinical appliances is also discussed.

Transcriptional mechanisms of drug addiction

Drugs of abuse can modify gene expression in brain reward and motivation centers, which contribute to the structural and functional remodeling of these circuits that impacts the emergence of a state of addiction. Our understanding of how addictive drugs induce transcriptomic plasticity in addiction-relevant brain regions, particularly in the striatum, has increased dramatically in recent years. Intracellular signaling machineries, transcription factors, chromatin modifications, and regulatory noncoding RNAs have all been implicated in the mechanisms through which addictive drugs act in the brain. Here, we briefly summarize some of the molecular mechanisms through which drugs of abuse can exert their transcriptional effects in the brain region, with an emphasis on the role for microRNAs in this process.


Nac1 promotes self-renewal of embryonic stem cells through direct transcriptional regulation of c-Myc

The pluripotency transcriptional network in embryonic stem cells (ESCs) is composed of distinct functional units including the core and Myc units. It is hoped that dissection of the cellular functions and interconnections of network factors will aid our understanding of ESC and cancer biology. Proteomic and genomic approaches have identified Nac1 as a member of the core pluripotency network. However, previous studies have predominantly focused on the role of Nac1 in psychomotor stimulant response and cancer pathogenesis. In this study, we report that Nac1 is a self-renewal promoting factor, but is not required for maintaining pluripotency of ESCs. Loss of function of Nac1 in ESCs results in a reduced proliferation rate and an enhanced differentiation propensity. Nac1 overexpression promotes ESC proliferation and delays ESC differentiation in the absence of leukemia inhibitory factor (LIF). Furthermore, we demonstrated that Nac1 directly binds to the c-Myc promoter and regulates c-Myc transcription. The study also revealed that the function of Nac1 in promoting ESC self-renewal appears to be partially mediated by c-Myc. These findings establish a functional link between the core and c-Myc-centered networks and provide new insights into mechanisms of stemness regulation in ESCs and cancer.

NAC1 Regulates Somatic Cell Reprogramming by Controlling Zeb1 and E-cadherin Expression

Reprogramming somatic cells to induced pluripotent stem cells (iPSCs) is a long and inefficient process. A thorough understanding of the molecular mechanisms underlying reprogramming is paramount for efficient generation and safe application of iPSCs in medicine. While intensive efforts have been devoted to identifying reprogramming facilitators and barriers, a full repertoire of such factors, as well as their mechanistic actions, is poorly defined. Here, we report that NAC1, a pluripotency-associated factor and NANOG partner, is required for establishment of pluripotency during reprogramming. Mechanistically, NAC1 is essential for proper expression of E-cadherin by a dual regulatory mechanism: it facilitates NANOG binding to the E-cadherin promoter and fine-tunes its expression; most importantly, it downregulates the E-cadherin repressor ZEB1 directly via transcriptional repression and indirectly via post-transcriptional activation of the miR-200 miRNAs. Our study thus uncovers a previously unappreciated role for the pluripotency regulator NAC1 in promoting efficient somatic cell reprogramming.

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NAC1 is critical for efficient iPSC generation

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NAC1 facilitates NANOG binding to E-cadherin promoter

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NAC1 binds to Zeb1 promoter and represses its expression

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NAC1 binds to the miR-200 loci and indirectly activates E-cadherin expression

Loss of NAC1 expression is associated with defective bony patterning in the murine vertebral axis

NAC1 encoded by NACC1 is a member of the BTB/POZ family of proteins and participates in several pathobiological processes. However, its function during tissue development has not been elucidated. In this study, we compared homozygous null mutant Nacc1^-/- and wild type Nacc1^+/+ mice to determine the consequences of diminished NAC1 expression. The most remarkable change in Nacc1^-/- mice was a vertebral patterning defect in which most knockout animals exhibited a morphological transformation of the sixth lumbar vertebra (L6) into a sacral identity; thus, the total number of pre-sacral vertebrae was decreased by one (to 25) in Nacc1^-/- mice. Heterozygous Nacc1^+/- mice had an increased tendency to adopt an intermediate phenotype in which L6 underwent partial sacralization. Nacc1^-/- mice also exhibited non-closure of the dorsal aspects of thoracic vertebrae T10-T12. Chondrocytes from Nacc1^+/+ mice expressed abundant NAC1 while Nacc1^-/- chondrocytes had undetectable levels. Loss of NAC1 in Nacc1^-/- mice was associated with significantly reduced chondrocyte migratory potential as well as decreased expression of matrilin-3 and matrilin-4, two cartilage-associated extracellular matrix proteins with roles in the development and homeostasis of cartilage and bone. These data suggest that NAC1 participates in the motility and differentiation of developing chondrocytes and cartilaginous tissues, and its expression is necessary to maintain normal axial patterning of murine skeleton.

Cocainomics: new insights into the molecular basis of cocaine addiction

Until recently, knowledge of the impact of abused drugs on gene and protein expression in the brain was limited to less than 100 targets. With the advent of high-throughput genomic and proteomic techniques, investigators are now able to evaluate changes across the entire genome and across thousands of proteins in defined brain regions and generate expression profiles of vulnerable neuroanatomical substrates in rodent and nonhuman primate drug abuse models and in human post-mortem brain tissue from drug abuse victims. The availability of gene and protein expression profiles will continue to expand our understanding of the short- and long-term consequences of drug addiction and other addictive disorders and may provide new approaches or new targets for pharmacotherapeutic intervention. This review summarizes several important genomic and proteomic studies of cocaine abuse/addiction from rodent, nonhuman primate, and human postmortem studies of cocaine abuse and explores how these studies have advanced our understanding of addiction.

The C-terminal pentapeptide of Nanog tryptophan repeat domain interacts with Nac1 and regulates stem cell proliferation but not pluripotency

Overexpression of Nanog in mouse embryonic stem (ES) cells has been shown to abrogate the requirement of leukemia inhibitory factor for self-renewal in culture. Little is known about the molecular mechanism of Nanog function. Here we describe the role of the tryptophan repeat (WR) domain, one of the two transactivators at its C terminus, in regulating stem cell proliferation as well as pluripotency. We first created a supertransactivator, W2W3x10, by duplicating repeats W2W3 10 times and discovered that it can functionally substitute for wild type WR at sustaining pluripotency, albeit with a significantly slower cell cycle, phenocopying Nanog(9W) with the C-terminal pentapeptide (WNAAP) of WR deleted. ES cells carrying both W2W3x10 and Nanog(9W) have a longer G1 phase, a shorter S phase in cell cycle distribution and progression analysis, and a lower level of pAkt(Ser473) compared with wild type Nanog, suggesting that both mutants impact the cell cycle machinery via the phosphatidylinositol 3-kinase/Akt pathway. Both mutants remain competent in dimerizing with Nanog but cannot form a complex with Nac1 efficiently, suggesting that WNAAP may be involved in Nac1 binding. By tagging Gal4DBD with WNAAP, we demonstrated that this pentapeptide is sufficient to confer Nac1 binding. Furthermore, we can rescue W2W3x10 by placing WNAAP at the corresponding locations. Finally, we found that Nanog and Nac1 synergistically up-regulate ERas expression and promote the proliferation of ES cells. These results suggest that Nanog interacts with Nac1 through WNAAP to regulate the cell cycle of ES cells via the ERas/phosphatidylinositol 3-kinase/Akt pathway, but not pluripotency, thus decoupling cell cycle control from pluripotency.

NAC-1 controls cell growth and survival by repressing transcription of Gadd45GIP1, a candidate tumor suppressor

Cancer mortality and morbidity are primarily related to recurrent tumors, and characterization of recurrence-associated genes should illuminate fundamental properties of tumor progression and provide new therapeutic targets. We have previously identified NAC-1, a member of the BTB/POZ gene family and a transcription repressor, as a gene associated with recurrent ovarian carcinomas after chemotherapy. We further showed that homodimerization of NAC-1 proteins is essential for tumor growth and survival. In this study, we applied serial analysis of gene expression and identified growth arrest and DNA-damage-inducible 45-gamma interacting protein (Gadd45GIP1) as one of the downstream genes negatively regulated by NAC-1. NAC-1 knockdown in both SKOV3 and HeLa cells that expressed abundant endogenous NAC-1 induced Gadd45GIP1 expression transcriptionally; on the other hand, engineered expression of NAC-1 in NAC-1-negative RK3E and HEK293 cells suppressed endogenous Gadd45GIP1 expression. In NAC-1-expressing tumor cells, induction of dominant negative NAC-1 conferred a growth-inhibitory effect that can be partially reversed by Gadd45GIP1 knockdown. Induced Gadd45GIP1 expression resulted in growth arrest in SKOV3 and HeLa cells both in vitro and in vivo. In summary, NAC-1 contributes to tumor growth and survival by at least inhibiting Gadd45GIP1 expression, which has a tumor suppressor effect in cancer cells.

NAC1 regulates the recruitment of the proteasome complex into dendritic spines

Coordinated proteolysis of synaptic proteins is required for synaptic plasticity, but a mechanism for recruiting the ubiquitin-proteasome system (UPS) into dendritic spines is not known. NAC1 is a cocaine-regulated transcriptional protein that was found to complex with proteins in the UPS, including cullins and Mov34. NAC1 and the proteasome were cotranslocated from the nucleus into dendritic spines in cortical neurons in response to proteasome inhibition or disinhibiting synaptic activity with bicuculline. Bicuculline also produced a progressive accumulation of the proteasome and NAC1 in the postsynaptic density. Recruitment of the proteasome into dendrites and postsynaptic density by bicuculline was prevented in neurons from mice harboring an NAC1 gene deletion or in neurons transfected with mutated NAC1 lacking the proteasome binding domain. These experiments show that NAC1 modulates the translocation of the UPS from the nucleus into dendritic spines, thereby suggesting a potential missing link in the recruitment of necessary proteolysis machinery for synaptic remodeling.

Requirement for the POZ/BTB protein NAC1 in acute but not chronic psychomotor stimulant response

NAC1 is a novel member of the POZ/BTB (Pox virus and Zinc finger/Bric-a-bracTramtrack Broad complex) but varies from other proteins of this class in that it lacks the characteristic DNA-binding motif, suggesting a novel role. We have employed constitutive gene deletion to elucidate the role of NAC1 in vivo. Nac1 mutant mice are viable with no obvious developmental or physiological impairments. Previous studies suggest a role for NAC1 in cocaine-mediated behaviors. Therefore, we evaluated a variety of behaviors associated with psychomotor stimulant effects in Nac1 mutant mice. Acute locomotor activating effects of cocaine or amphetamine are absent in Nac1 mutant mice, however longer exposure to these psychomotor stimulants result in the development of behavioral sensitization. Acute rewarding properties of cocaine and amphetamine are also blunted in mutant mice, yet repeated exposure resulted in conditioned place preference similar to that observed in wild-type mice. Lastly, increases in extracellular dopamine in the nucleus accumbens, which accompany acute cocaine administration, are blunted in mutant mice, but following chronic cocaine extracellular dopamine levels are increased to the same extent as in wild-type mice. Together these data indicate involvement of NAC1 in the acute behavioral and neurochemical responses to psychomotor stimulants.

A protein interaction network for pluripotency of embryonic stem cells

Embryonic stem (ES) cells are pluripotent and of therapeutic potential in regenerative medicine. Understanding pluripotency at the molecular level should illuminate fundamental properties of stem cells and the process of cellular reprogramming. Through cell fusion the embryonic cell phenotype can be imposed on somatic cells, a process promoted by the homeodomain protein Nanog, which is central to the maintenance of ES cell pluripotency. Nanog is thought to function in concert with other factors such as Oct4 (ref. 8) and Sox2 (ref. 9) to establish ES cell identity. Here we explore the protein network in which Nanog operates in mouse ES cells. Using affinity purification of Nanog under native conditions followed by mass spectrometry, we have identified physically associated proteins. In an iterative fashion we also identified partners of several Nanog-associated proteins (including Oct4), validated the functional relevance of selected newly identified components and constructed a protein interaction network. The network is highly enriched for nuclear factors that are individually critical for maintenance of the ES cell state and co-regulated on differentiation. The network is linked to multiple co-repressor pathways and is composed of numerous proteins whose encoding genes are putative direct transcriptional targets of its members. This tight protein network seems to function as a cellular module dedicated to pluripotency.

Stress up-regulates neuronal expression of the herpes simplex virus type 2 large subunit of ribonucleotide reductase (R1; ICP10) by activating activator protein 1

Herpes simplex virus type 2 (HSV-2) genes expressed in neuronal cells in response to stress stimuli that trigger latency reactivation are largely unknown. Using a chloramphenicol acetyltransferase (CAT) reporter assay we found that stress caused a significant (P < .001) increase in ICP10 expression in neuronal cells. Up-regulation correlated with activator protein (AP)-1 activation, notably c-Jun and c-Fos that bind cognate elements in the ICP10 promoter. It was blocked by mutation of the AP-1 motifs in the ICP10 promoter. ICP10 expression protected neuronal cells from stress-induced apoptosis. The data suggest that ICP10 may contribute to HSV-2 reactivation by increasing neuronal survival.

Activity-dependent subcellular localization of NAC1

The expression of the transcriptional regulator NAC1 is increased in the nucleus accumbens of rats withdrawn from cocaine self-administration, and in vivo studies indicate that the up-regulation is a compensatory mechanism opposing the acute effects of cocaine. Both mammalian two-hybrid assay and punctate localization largely in the nucleus suggest NAC1 is a transcriptional regulator. However, in this report it is shown that in differentiated PC12 and Neuro2A cells, as well as in primary cortical neurons, NAC1 is diffusely expressed not only in the cell nucleus but also in cytoplasm. Blockade of spontaneous electrical activity by tetrodotoxin prevented the diffuse expression of NAC1, and depolarization with high potassium concentrations induced diffuse cellular localization in non-differentiating cells. The use of protein kinase C (PKC) inhibitors and activator, as well as the systematic mutation of potential PKC phosphorylation sites in NAC1, demonstrated that phosphorylation of residue S245 by PKC is a necessary event inducing diffuse NAC1 expression outside of the nucleus. These observations indicate a potential non-transcriptional role for NAC1 in the brain.

Molecular mechanisms of drug addiction

Regulation of gene expression is one mechanism by which drugs of abuse can induce relatively long-lasting changes in the brain to cause a state of addiction. Here, we focus on two transcription factors, CREB (cAMP response element binding protein) and DeltaFosB, which contribute to drug-induced changes in gene expression. Both are activated in the nucleus accumbens, a major brain reward region, but mediate different aspects of the addicted state. CREB mediates a form of tolerance and dependence, which dampens an individual's sensitivity to subsequent drug exposure and contributes to a negative emotional state during early phases of withdrawal. In contrast, DeltaFosB mediates a state of relatively prolonged sensitization to drug exposure and may contribute to the increased drive and motivation for drug, which is a core symptom of addictive disorders. A major goal of current research is to identify the many target genes through which CREB and DeltaFosB mediate these behavioral states. In addition, future work needs to understand how CREB and DeltaFosB, acting in concert with numerous other drug-induced molecular changes in nucleus accumbens and many other brain regions, interact with one another to produce the complex behavioral phenotype that defines addiction.