Drosophila Fezf functions as a transcriptional repressor to direct layer-specific synaptic connectivity in the fly visual system

The layered compartmentalization of synaptic connections, a common feature of nervous systems, underlies proper connectivity between neurons and enables parallel processing of neural information. However, the stepwise development of layered neuronal connections is not well understood. The medulla neuropil of the Drosophila visual system, which comprises 10 discrete layers (M1 to M10), where neural computations underlying distinct visual features are processed, serves as a model system for understanding layered synaptic connectivity. The first step in establishing layer-specific connectivity in the outer medulla (M1 to M6) is the innervation by lamina (L) neurons of one of two broad, primordial domains that will subsequently expand and transform into discrete layers. We previously found that the transcription factor dFezf cell-autonomously directs L3 lamina neurons to their proper primordial broad domain before they form synapses within the developing M3 layer. Here, we show that dFezf controls L3 broad domain selection through temporally precise transcriptional repression of the transcription factor slp1 (sloppy paired 1). In wild-type L3 neurons, slp1 is transiently expressed at a low level during broad domain selection. When dFezf is deleted, slp1 expression is up-regulated, and ablation of slp1 fully rescues the defect of broad domain selection in dFezf-null L3 neurons. Although the early, transient expression of slp1 is expendable for broad domain selection, it is surprisingly necessary for the subsequent L3 innervation of the M3 layer. DFezf thus functions as a transcriptional repressor to coordinate the temporal dynamics of a transcriptional cascade that orchestrates sequential steps of layer-specific synapse formation.

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Control of synaptic specificity by limiting promiscuous synapse formation

10.1101/415695 ◽

2018 ◽

Cited By ~ 2

Author(s):

Chundi Xu ◽

Emma Theisen ◽

Elijah Rumbaut ◽

Bryan Shum ◽

Jing Peng ◽

...

Keyword(s):

Visual System ◽

Synapse Formation ◽

Neural Circuits ◽

Local Environment ◽

Cell Types ◽

Partner Choice ◽

Synaptic Connectivity ◽

Specific Cell ◽

Synaptic Specificity ◽

And Function

SUMMARYThe ability of neurons to distinguish appropriate from inappropriate synaptic partners in their local environment is fundamental to the proper assembly and function of neural circuits. How synaptic partner selection is regulated is a longstanding question in Neurobiology. A prevailing hypothesis is that appropriate partners express complementary molecules that match them together and promote synaptogenesis. Dpr and DIP IgSF proteins bind heterophilically and are expressed in a complementary manner between synaptic partners in the Drosophila visual system. Here, we show that in the lamina, DIP mis-expression is sufficient to promote synapse formation with Dpr-expressing neurons, and that DIP proteins are not necessary for synaptogenesis but rather function to prevent ectopic synapse formation. These findings indicate that Dpr-DIP interactions regulate synaptic specificity by biasing synapse formation towards specific cell-types. We propose that synaptogenesis occurs independent of synaptic partner choice, and that precise synaptic connectivity is established by limiting promiscuous synapse formation.

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Loss of FOXF1 expression promotes human lung-resident mesenchymal stromal cell migration via ATX/LPA/LPA1 signaling axis

Scientific Reports ◽

10.1038/s41598-020-77601-1 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Pengxiu Cao ◽

Natalie M. Walker ◽

Russell R. Braeuer ◽

Serina Mazzoni-Putman ◽

Yoshiro Aoki ◽

...

Keyword(s):

Mesenchymal Stromal Cells ◽

Stromal Cells ◽

Transcriptional Repression ◽

Inflammatory Responses ◽

Transcriptional Repressor ◽

Boyden Chamber ◽

Signaling Axis ◽

Lpa1 Receptor ◽

Human Adult Lung ◽

Upregulated Genes

AbstractForkhead box F1 (FOXF1) is a lung embryonic mesenchyme-associated transcription factor that demonstrates persistent expression into adulthood in mesenchymal stromal cells. However, its biologic function in human adult lung-resident mesenchymal stromal cells (LR-MSCs) remain to be elucidated. Here, we demonstrate that FOXF1 expression acts as a restraint on the migratory function of LR-MSCs via its role as a novel transcriptional repressor of autocrine motility-stimulating factor Autotaxin (ATX). Fibrotic human LR-MSCs demonstrated lower expression of FOXF1 mRNA and protein, compared to non-fibrotic controls. RNAi-mediated FOXF1 silencing in LR-MSCs was associated with upregulation of key genes regulating proliferation, migration, and inflammatory responses and significantly higher migration were confirmed in FOXF1-silenced LR-MSCs by Boyden chamber. ATX is a secreted lysophospholipase D largely responsible for extracellular lysophosphatidic acid (LPA) production, and was among the top ten upregulated genes upon Affymetrix analysis. FOXF1-silenced LR-MSCs demonstrated increased ATX activity, while mFoxf1 overexpression diminished ATX expression and activity. The FOXF1 silencing-induced increase in LR-MSC migration was abrogated by genetic and pharmacologic targeting of ATX and LPA1 receptor. Chromatin immunoprecipitation analyses identified three putative FOXF1 binding sites in the 1.5 kb ATX promoter which demonstrated transcriptional repression of ATX expression. Together these findings identify FOXF1 as a novel transcriptional repressor of ATX and demonstrate that loss of FOXF1 promotes LR-MSC migration via the ATX/LPA/LPA1 signaling axis.

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High-throughput single-cell chromatin accessibility CRISPR screens enable unbiased identification of regulatory networks in cancer

Nature Communications ◽

10.1038/s41467-021-23213-w ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Sarah E. Pierce ◽

Jeffrey M. Granja ◽

William J. Greenleaf

Keyword(s):

Transcription Factor ◽

Single Cell ◽

Cancer Cells ◽

High Throughput ◽

Regulatory Networks ◽

Temporal Dynamics ◽

Chromatin Accessibility ◽

Regulatory Regions ◽

Factor Binding ◽

Genome Wide

AbstractChromatin accessibility profiling can identify putative regulatory regions genome wide; however, pooled single-cell methods for assessing the effects of regulatory perturbations on accessibility are limited. Here, we report a modified droplet-based single-cell ATAC-seq protocol for perturbing and evaluating dynamic single-cell epigenetic states. This method (Spear-ATAC) enables simultaneous read-out of chromatin accessibility profiles and integrated sgRNA spacer sequences from thousands of individual cells at once. Spear-ATAC profiling of 104,592 cells representing 414 sgRNA knock-down populations reveals the temporal dynamics of epigenetic responses to regulatory perturbations in cancer cells and the associations between transcription factor binding profiles.

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Repression of ESR1 through Actions of Estrogen Receptor Alpha and Sin3A at the Proximal Promoter

Molecular and Cellular Biology ◽

10.1128/mcb.00383-09 ◽

2009 ◽

Vol 29 (18) ◽

pp. 4949-4958 ◽

Cited By ~ 47

Author(s):

Stephanie J. Ellison-Zelski ◽

Natalia M. Solodin ◽

Elaine T. Alarid

Keyword(s):

Gene Expression ◽

Estrogen Receptor ◽

Transcription Factor ◽

Rna Polymerase Ii ◽

Transcriptional Repression ◽

Estrogen Receptor Alpha ◽

Proximal Promoter ◽

Receptor Alpha ◽

Expression Of Genes ◽

Activation Of Transcription

ABSTRACT Gene expression results from the coordinated actions of transcription factor proteins and coregulators. Estrogen receptor alpha (ERα) is a ligand-activated transcription factor that can both activate and repress the expression of genes. Activation of transcription by estrogen-bound ERα has been studied in detail, as has antagonist-induced repression, such as that which occurs by tamoxifen. How estrogen-bound ERα represses gene transcription remains unclear. In this report, we identify a new mechanism of estrogen-induced transcriptional repression by using the ERα gene, ESR1. Upon estrogen treatment, ERα is recruited to two sites on ESR1, one distal (ENH1) and the other at the proximal (A) promoter. Coactivator proteins, namely, p300 and AIB1, are found at both ERα-binding sites. However, recruitment of the Sin3A repressor, loss of RNA polymerase II, and changes in histone modifications occur only at the A promoter. Reduction of Sin3A expression by RNA interference specifically inhibits estrogen-induced repression of ESR1. Furthermore, an estrogen-responsive interaction between Sin3A and ERα is identified. These data support a model of repression wherein actions of ERα and Sin3A at the proximal promoter can overcome activating signals at distal or proximal sites and ultimately decrease gene expression.

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The ETO Protein Disrupted in t(8;21)-Associated Acute Myeloid Leukemia Is a Corepressor for the Promyelocytic Leukemia Zinc Finger Protein

Molecular and Cellular Biology ◽

10.1128/mcb.20.6.2075-2086.2000 ◽

2000 ◽

Vol 20 (6) ◽

pp. 2075-2086 ◽

Cited By ~ 98

Author(s):

Ari M. Melnick ◽

Jennifer J. Westendorf ◽

Adam Polinger ◽

Graeme W. Carlile ◽

Sally Arai ◽

...

Keyword(s):

Acute Myeloid Leukemia ◽

Transcription Factor ◽

Zinc Finger ◽

Transcriptional Repression ◽

Histone Deacetylases ◽

Myeloid Leukemia ◽

Histone Deacetylase Inhibitors ◽

Promyelocytic Leukemia ◽

Promyelocytic Leukemia Zinc Finger ◽

Acute Myeloid

ABSTRACT The ETO protein was originally identified by its fusion to the AML-1 transcription factor in translocation (8;21) associated with the M2 form of acute myeloid leukemia (AML). The resulting AML-1–ETO fusion is an aberrant transcriptional regulator due to the ability of ETO, which does not bind DNA itself, to recruit the transcriptional corepressors N-CoR, SMRT, and Sin3A and histone deacetylases. The promyelocytic leukemia zinc finger (PLZF) protein is a sequence-specific DNA-binding transcriptional factor fused to retinoic acid receptor α in acute promyelocytic leukemia associated with the (11;17)(q23;q21) translocation. PLZF also mediates transcriptional repression through the actions of corepressors and histone deacetylases. We found that ETO is one of the corepressors recruited by PLZF. The PLZF and ETO proteins associate in vivo and in vitro, and ETO can potentiate transcriptional repression by PLZF. The N-terminal portion of ETO forms complexes with PLZF, while the C-terminal region, which was shown to bind to N-CoR and SMRT, is required for the ability of ETO to augment transcriptional repression by PLZF. The second repression domain (RD2) of PLZF, not the POZ/BTB domain, is necessary to bind to ETO. Corepression by ETO was completely abrogated by histone deacetylase inhibitors. This identifies ETO as a cofactor for a sequence-specific transcription factor and indicates that, like other corepressors, it functions through the action of histone deactylase.

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The megakaryocytic transcription factor ARID3A suppresses leukemia pathogenesis

Blood ◽

10.1182/blood.2021012231 ◽

2021 ◽

Author(s):

Oriol Alejo-Valle ◽

Karoline Weigert ◽

Raj Bhayadia ◽

Michelle Ng ◽

Hasan Issa ◽

...

Keyword(s):

Transcription Factor ◽

Transcriptional Repression ◽

Reverse Genetics ◽

Erythroid Differentiation ◽

Chromosome 21 ◽

Hematopoietic Stem ◽

Megakaryocytic Differentiation ◽

Megakaryoblastic Leukemia ◽

Multiple Routes ◽

Induced Apoptosis

Given the plasticity of hematopoietic stem/progenitor cells, multiple routes of differentiation must be blocked during acute myeloid leukemia pathogenesis - the molecular basis of which is incompletely understood. Here we report that post-transcriptional repression of the transcription factor ARID3A by miR-125b is a key event in megakaryoblastic leukemia (AMKL) pathogenesis. AMKL is frequently associated with trisomy 21 and GATA1 mutations (GATA1s), and children with Down syndrome are at a high risk of developing this disease. We show that chromosome 21-encoded miR-125b synergizes with Gata1s to drive leukemogenesis in this context. Leveraging forward and reverse genetics, we uncover Arid3a as the main miR-125b target behind this synergy. We demonstrate that, during normal hematopoiesis, this transcription factor promotes megakaryocytic differentiation in concert with GATA1 and mediates TGFβ-induced apoptosis and cell cycle arrest in complex with SMAD2/3. While Gata1s mutations perturb erythroid differentiation and induce hyperproliferation of megakaryocytic progenitors, intact ARID3A expression assures their megakaryocytic differentiation and growth restriction. Upon knockdown, these tumor suppressive functions are revoked, causing a dual megakaryocytic/erythroid differentiation blockade and subsequently AMKL. Inversely, restoring ARID3A expression relieves the megakaryocytic differentiation arrest in AMKL patient-derived xenografts. This work illustrates how mutations in lineage-determining transcription factors and perturbation of post-transcriptional gene regulation can interplay to block multiple routes of hematopoietic differentiation and cause leukemia. In AMKL, surmounting this differentiation blockade through restoration of the tumor suppressor ARID3A represents a promising strategy for treating this lethal pediatric disease.

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Functional Domains of c-myc Promoter Binding Protein 1 Involved in Transcriptional Repression and Cell Growth Regulation

Molecular and Cellular Biology ◽

10.1128/mcb.19.4.2880 ◽

1999 ◽

Vol 19 (4) ◽

pp. 2880-2886 ◽

Cited By ~ 31

Author(s):

Asish K. Ghosh ◽

Robert Steele ◽

Ratna B. Ray

Keyword(s):

Amino Acids ◽

Cell Growth ◽

Dna Binding ◽

Transcriptional Repression ◽

Growth Regulation ◽

Transcriptional Repressor ◽

Binding Domain ◽

Dna Binding Domain ◽

Repressor Activity

ABSTRACT We initially identified c-myc promoter binding protein 1 (MBP-1), which negatively regulates c-myc promoter activity, from a human cervical carcinoma cell expression library. Subsequent studies on the biological role of MBP-1 demonstrated induction of cell death in fibroblasts and loss of anchorage-independent growth, reduced invasive ability, and tumorigenicity of human breast carcinoma cells. To investigate the potential role of MBP-1 as a transcriptional regulator, a chimeric protein containing MBP-1 fused to the DNA binding domain of the yeast transactivator factor GAL4 was constructed. This fusion protein exhibited repressor activity on the herpes simplex virus thymidine kinase promoter via upstream GAL4 DNA binding sites. Structure-function analysis of mutant MBP-1 in the context of the GAL4 DNA binding domain revealed that MBP-1 transcriptional repressor domains are located in the N terminus (amino acids 1 to 47) and C terminus (amino acids 232 to 338), whereas the activation domain lies in the middle (amino acids 140 to 244). The N-terminal domain exhibited stronger transcriptional repressor activity than the C-terminal region. When the N-terminal repressor domain was transferred to a potent activator, transcription was strongly inhibited. Both of the repressor domains contained hydrophobic regions and had an LXVXL motif in common. Site-directed mutagenesis in the repressor domains indicated that the leucine residues in the LXVXL motif are required for transcriptional repression. Mutation of the leucine residues in the common motif of MBP-1 also abrogated the repressor activity on the c-mycpromoter. In addition, the leucine mutant forms of MBP-1 failed to suppress cell growth in fibroblasts like wild-type MBP-1. Taken together, our results indicate that MBP-1 is a complex cellular factor containing multiple transcriptional regulatory domains that play an important role in cell growth regulation.

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A novel role for an antioxidant transcription factor Nrf2 as a transcriptional repressor of the circadian molecular clock

Free Radical Biology and Medicine ◽

10.1016/j.freeradbiomed.2021.08.103 ◽

2021 ◽

Vol 177 ◽

pp. S84

Author(s):

Elizabeth Sutton ◽

Alan Carter ◽

Sandra Fawcett ◽

Damilola Sarumi ◽

Ian Copple ◽

...

Keyword(s):

Transcription Factor ◽

Molecular Clock ◽

Transcriptional Repressor

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Mechanisms of mammalian zinc-regulated gene expression

Biochemical Society Transactions ◽

10.1042/bst0361262 ◽

2008 ◽

Vol 36 (6) ◽

pp. 1262-1266 ◽

Cited By ~ 38

Author(s):

Kelly A. Jackson ◽

Ruth A. Valentine ◽

Lisa J. Coneyworth ◽

John C. Mathers ◽

Dianne Ford

Keyword(s):

Gene Expression ◽

Transcription Factor ◽

Transcriptional Repression ◽

Mammalian Cells ◽

Gene Promoter ◽

Mrna Levels ◽

Promoter Regions ◽

Mrna Stabilization ◽

Transcriptional Regulatory ◽

Regulated Gene Expression

Mechanisms through which gene expression is regulated by zinc are central to cellular zinc homoeostasis. In this context, evidence for the involvement of zinc dyshomoeostasis in the aetiology of diseases, including Type 2 diabetes, Alzheimer's disease and cancer, highlights the importance of zinc-regulated gene expression. Mechanisms elucidated in bacteria and yeast provide examples of different possible modes of zinc-sensitive gene regulation, involving the zinc-regulated binding of transcriptional activators and repressors to gene promoter regions. A mammalian transcriptional regulatory mechanism that mediates zinc-induced transcriptional up-regulation, involving the transcription factor MTF1 (metal-response element-binding transcription factor 1), has been studied extensively. Gene responses in the opposite direction (reduced mRNA levels in response to increased zinc availability) have been observed in mammalian cells, but a specific transcriptional regulatory process responsible for such a response has yet to be identified. Examples of single zinc-sensitive transcription factors regulating gene expression in opposite directions are emerging. Although zinc-induced transcriptional repression by MTF1 is a possible explanation in some specific instances, such a mechanism cannot account for repression by zinc of all mammalian genes that show this mode of regulation, indicating the existence of as yet uncharacterized mechanisms of zinc-regulated transcription in mammalian cells. In addition, recent findings reveal a role for effects of zinc on mRNA stability in the regulation of specific zinc transporters. Our studies on the regulation of the human gene SLC30A5 (solute carrier 30A5), which codes for the zinc transporter ZnT5, have revealed that this gene provides a model system by which to study both zinc-induced transcriptional down-regulation and zinc-regulated mRNA stabilization.

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