scholarly journals Functional differences between HOX proteins conferred by two residues in the homeodomain N-terminal arm.

1994 ◽  
Vol 14 (8) ◽  
pp. 5066-5075 ◽  
Author(s):  
M L Phelan ◽  
R Sadoul ◽  
M S Featherstone
Keyword(s):  
Dna Binding ◽  
Transcriptional Activation ◽  
Hox Genes ◽  
Functional Difference ◽  
Recognition Sequence ◽  
Embryonic Axes ◽  
Alpha Helices ◽  
Core Motif ◽  
Hox Gene ◽  
Positional Identity

Hox genes encode homeodomain-containing transcriptional regulators that function during development to specify positional identity along embryonic axes. The homeodomain is composed of a flexible N-terminal arm and three alpha helices, and it differentially binds DNA. A number of homeodomains recognize sites containing a TAAT core motif. The product of the murine Hoxd-4 (Hox-4.2) gene functions in a positive autoregulatory fashion in P19 cells that is dependent on two TAAT motifs in the Hoxd-4 promoter. This effect is specific in that murine HOXA-1 (HOX-1.6) is unable to activate transcription through the Hoxd-4 autoregulatory element. Here we show that this is due to an inability of the HOXA-1 homeodomain to bind a HOXD-4 recognition site effectively. We have produced chimeras between HOXD-4 and HOXA-1 to map specific residues responsible for this functional difference. When positions 2 and 3 in the N-terminal arm of HOXA-1 were converted to HOXD-4 identity, both strong DNA binding and transcriptional activation were rescued. This substitution appears to confer an increased DNA-binding ability on the HOXA-1 homeodomain, since we were unable to detect a high-affinity recognition sequence for HOXA-1 in a randomized pool of DNA probes. The contribution of position 3 to DNA binding has been implicated by structural studies, but this is the first report of the importance of position 2 in regulating homeodomain-DNA interactions. Additionally, specific homeodomain residues that confer major differences in DNA binding and transcriptional activation between Hox gene products have not been previously determined. Identity at these two positions is generally conserved among paralogs but varies between Hox gene subfamilies. As a result, these residues may be important for the regulation of target gene expression by specific Hox products.

Functional differences between HOX proteins conferred by two residues in the homeodomain N-terminal arm

1994 ◽  
Vol 14 (8) ◽  
pp. 5066-5075
Author(s):  
M L Phelan ◽  
R Sadoul ◽  
M S Featherstone
Keyword(s):  
Dna Binding ◽  
Transcriptional Activation ◽  
Hox Genes ◽  
Functional Difference ◽  
Recognition Sequence ◽  
Embryonic Axes ◽  
Alpha Helices ◽  
Core Motif ◽  
Hox Gene ◽  
Positional Identity

Hox genes encode homeodomain-containing transcriptional regulators that function during development to specify positional identity along embryonic axes. The homeodomain is composed of a flexible N-terminal arm and three alpha helices, and it differentially binds DNA. A number of homeodomains recognize sites containing a TAAT core motif. The product of the murine Hoxd-4 (Hox-4.2) gene functions in a positive autoregulatory fashion in P19 cells that is dependent on two TAAT motifs in the Hoxd-4 promoter. This effect is specific in that murine HOXA-1 (HOX-1.6) is unable to activate transcription through the Hoxd-4 autoregulatory element. Here we show that this is due to an inability of the HOXA-1 homeodomain to bind a HOXD-4 recognition site effectively. We have produced chimeras between HOXD-4 and HOXA-1 to map specific residues responsible for this functional difference. When positions 2 and 3 in the N-terminal arm of HOXA-1 were converted to HOXD-4 identity, both strong DNA binding and transcriptional activation were rescued. This substitution appears to confer an increased DNA-binding ability on the HOXA-1 homeodomain, since we were unable to detect a high-affinity recognition sequence for HOXA-1 in a randomized pool of DNA probes. The contribution of position 3 to DNA binding has been implicated by structural studies, but this is the first report of the importance of position 2 in regulating homeodomain-DNA interactions. Additionally, specific homeodomain residues that confer major differences in DNA binding and transcriptional activation between Hox gene products have not been previously determined. Identity at these two positions is generally conserved among paralogs but varies between Hox gene subfamilies. As a result, these residues may be important for the regulation of target gene expression by specific Hox products.

scholarly journals The t(8;21) fusion protein interferes with AML-1B-dependent transcriptional activation.

1995 ◽  
Vol 15 (4) ◽  
pp. 1974-1982 ◽  
Author(s):  
S Meyers ◽  
N Lenny ◽  
S W Hiebert
Keyword(s):  
Dna Binding ◽  
Transcriptional Activation ◽  
Chimeric Protein ◽  
Cell Receptor ◽  
Subcellular Fractionation ◽  
Myelogenous Leukemia ◽  
Core Motif ◽  
Acute Myelogenous ◽  
Beta Enhancer ◽  
A Site

The AML-1/CBF beta transcription factor complex is targeted by both the t(8;21) and the inv(16) chromosomal alterations, which are frequently observed in acute myelogenous leukemia. AML-1 is a site-specific DNA-binding protein that recognizes the enhancer core motif TGTGGT. The t(8;21) translocation fuses the first 177 amino acids of AML-1 to MTG8 (also known as ETO), generating a chimeric protein that retains the DNA-binding domain of AML-1. Analysis of endogenous AML-1 DNA-binding complexes suggested the presence of at least two AML-1 isoforms. Accordingly, we screened a human B-cell cDNA library and isolated a larger, potentially alternatively spliced, form of AML1, termed AML1B. AML-1B is a protein of 53 kDa that binds to a consensus AML-1-binding site and complexes with CBF beta. Subcellular fractionation experiments demonstrated that both AML-1 and AML-1/ETO are efficiently extracted from the nucleus under ionic conditions but that AML-1B is localized to a salt-resistant nuclear compartment. Analysis of the transcriptional activities of AML-1, AML-1B, and AML-1/ETO demonstrated that only AML-1B activates transcription from the T-cell receptor beta enhancer. Mixing experiments indicated that AML-1/ETO can efficiently block AML-1B-dependent transcriptional activation, suggesting that the t(8;21) translocation creates a dominant interfering protein.

scholarly journals Methylation in HOX Clusters and Its Applications in Cancer Therapy

Cells ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 1613 ◽  
Author(s):  
Ana Paço ◽  
Simone Aparecida de Bessa Garcia ◽  
Renata Freitas
Keyword(s):  
Gene Expression ◽  
Cancer Therapy ◽  
Hox Genes ◽  
Treatment Options ◽  
Chemotherapy Resistance ◽  
Migration And Invasion ◽  
Aberrant Expression ◽  
Hox Gene ◽  
Positional Identity ◽  
Near Future

HOX genes are commonly known for their role in embryonic development, defining the positional identity of most structures along the anterior–posterior axis. In postembryonic life, HOX gene aberrant expression can affect several processes involved in tumorigenesis such as proliferation, apoptosis, migration and invasion. Epigenetic modifications are implicated in gene expression deregulation, and it is accepted that methylation events affecting HOX gene expression play crucial roles in tumorigenesis. In fact, specific methylation profiles in the HOX gene sequence or in HOX-associated histones are recognized as potential biomarkers in several cancers, helping in the prediction of disease outcomes and adding information for decisions regarding the patient’s treatment. The methylation of some HOX genes can be associated with chemotherapy resistance, and its identification may suggest the use of other treatment options. The use of epigenetic drugs affecting generalized or specific DNA methylation profiles, an approach that now deserves much attention, seems likely to be a promising weapon in cancer therapy in the near future. In this review, we summarize these topics, focusing particularly on how the regulation of epigenetic processes may be used in cancer therapy.

scholarly journals The pentapeptide motif of Hox proteins is required for cooperative DNA binding with Pbx1, physically contacts Pbx1, and enhances DNA binding by Pbx1.

1995 ◽  
Vol 15 (10) ◽  
pp. 5811-5819 ◽  
Author(s):  
P S Knoepfler ◽  
M P Kamps
Keyword(s):  
Dna Binding ◽  
Hox Genes ◽  
Mutational Analysis ◽  
Wild Type ◽  
Homeodomain Proteins ◽  
Binding Ability ◽  
Hox Proteins ◽  
Positional Identity ◽  
Methionine Residues ◽  
Anterior Posterior

The vertebrate Hox genes, which represent a subset of all homeobox genes, encode proteins that regulate anterior-posterior positional identity during embryogenesis and are cognates of the Drosophila homeodomain proteins encoded by genes composing the homeotic complex (HOM-C). Recently, we demonstrated that multiple Hox proteins bind DNA cooperatively with both Pbx1 and its oncogenic derivative, E2A-Pbx1. Here, we show that the highly conserved pentapeptide motif F/Y-P-W-M-R/K, which occurs in numerous Hox proteins and is positioned 8 to 50 amino acids N terminal to the homeodomain, is essential for cooperative DNA binding with Pbx1 and E2A-Pbx1. Point mutational analysis demonstrated that the tryptophan and methionine residues within the core of this motif were critical for cooperative DNA binding. A peptide containing the wild-type pentapeptide sequence, but not one in which phenylalanine was substituted for tryptophan, blocked the ability of Hox proteins to bind cooperatively with Pbx1 or E2A-Pbx1, suggesting that the pentapeptide itself provides at least one surface through which Hox proteins bind Pbx1. Furthermore, the same peptide, but not the mutant peptide, stimulated DNA binding by Pbx1, suggesting that interaction of Hox proteins with Pbx1 through the pentapeptide motif raises the DNA-binding ability of Pbx1.

Mechanisms of Leukemogenesis by MLL-CALM: Characterization of a CALM-Derived Transcriptional Regulatory Domain.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 3387-3387
Author(s):  
Mwe Mwe Chao ◽  
Emily J. Fox ◽  
Daniel S. Wechsler
Keyword(s):  
Dna Binding ◽  
Transcriptional Activation ◽  
Nuclear Export ◽  
Transcriptional Activity ◽  
Hox Genes ◽  
Luciferase Activity ◽  
Expression Vectors ◽  
Luciferase Reporter ◽  
Fusion Partner ◽  
Cytoplasmic Localization

Abstract Background: MLL translocations are common in infant leukemias, and >50 distinct translocation partners have been described. We recently identified the CALM gene as a novel MLL partner in an infant with aggressive AML. Interestingly, CALM was first discovered as a translocation partner for AF10, which had previously been identified as an MLL fusion partner in aggressive leukemias and lymphomas. The native CALM protein exhibits predominantly cytoplasmic localization, and participates in clathrin-dependent endocytosis and intracellular vesicle transport. We have previously shown that expression of MLL-CALM immortalizes murine hematopoietic progenitors, and that fusion of the carboxy terminus of CALM to MLL alters MLL transcriptional activity. We hypothesize that CALM possesses a specific transcriptional activation domain (TAD) which modulates MLL transcriptional activity of HOX genes, thereby contributing to leukemogenesis. Objectives: 1) To determine whether native CALM localizes to the nucleus, 2) To delineate specific CALM domains which constitute the CALM TAD, and 3) To determine whether MLL-CALM activates transcription through the murine HOXA7 promoter. Methods: Human fibroblast cells were treated with Leptomycin B (an antifungal antibiotic which specifically inhibits nuclear export) and stained with an anti-CALM antibody. We prepared a set of expression vectors in which various portions of CALM are fused to a GAL4 DNA-binding domain. These vectors were co-transfected with a GAL4-luciferase reporter plasmid into COS7 cells, and luciferase activity was measured 48 hours after transient transfection. Luciferase assays were also performed using MSCV-MLL-CALM or MSCV-CALM plasmids co-transfected with a HOXA7 promoter-luciferase reporter construct. Results: After inhibition of nuclear export, native CALM localized to both the nucleus and cytoplasm. Significant luciferase activity was only observed with constructs containing distal CALM carboxy amino acids (aa 436–660). Mutation of an NR (Nuclear Receptor) Box motif (aa 510–514) did not affect CALM-dependent transcription. We found that two endocytosis-related NPF domains play opposite roles: deletion of NPF#1 (aa 437–439) dramatically reduced, while mutation of NPF#2 (aa 639–641) increased transcriptional activity. Expression constructs lacking GAL4 DNA binding domains had no effect on transcription, and GAL4 binding sites were required for luciferase activity in this system. Finally, MLL-CALM activated transcription of the murine HOXA7 promoter in comparison with native CALM or empty vector. Conclusions: We have confirmed that native CALM is able to localize to the nucleus, and we have begun to identify specific critical residues in the CALM TAD. The presence of a CALM TAD in MLL-CALM suggests that altered transcriptional regulation of MLL-dependent HOX genes may play an important role in MLL-CALM dependent transformation. Our observations raise the possibility that other MLL partners with native cytoplasmic localization may possess unrecognized transcriptional activity, and provide new insight into both MLL-CALM and CALM-AF10 mediated leukemogenesis.

Menin Regulates the Function of Lymphoid Progenitors and Hematopoietic Stem Cells.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 1257-1257
Author(s):  
Ivan Maillard ◽  
Ya-Xiong Chen ◽  
Anthony T. Tubbs ◽  
Olga Shestova ◽  
Warren S. Pear ◽  
...  
Keyword(s):  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Malignant Transformation ◽  
Transcriptional Activation ◽  
Hox Genes ◽  
Type I ◽  
Hematopoietic Stem ◽  
Hox Gene ◽  
Men1 Gene ◽  
Mll Gene

Abstract Menin is the product of the Men1 gene, a tumor suppressor gene that is mutated in patients with multiple endocrine neoplasia type I (MEN1). In addition to its effects in endocrine tissues, Menin interacts with the Mixed Lineage Leukemia (Mll) gene product as part of a multiprotein complex with H3K4 methyltransferase activity. Menin is required to mediate malignant transformation induced by Mll gene rearrangements, an activity associated with transcriptional activation of Homeobox (Hox) gene expression, presumably through epigenetic regulation. To explore the normal function of Menin in hematopoiesis, we studied bone marrow (BM) progenitors after inactivation of the Men1 gene in adult mice. Loss of Menin led to a modest reduction in peripheral blood neutrophil, lymphocyte and platelet counts. In the absence of hematopoietic stress, numbers of multilineage and myeloerythroid BM progenitors were preserved, but pro-B cells and downstream B lineage progenitor subsets were significantly decreased. Competitive BM transplantation assays revealed a marked defect in the function of Menin-deficient hematopoietic stem cells (HSCs), including long-term HSCs. Furthermore, Menin-deficient mice had impaired hematopoietic recovery after chemoablation with 5-fluorouracil. However, expression of Hox genes in BM HSCs was not impaired in the absence of Menin. These observations reveal an essential role of Menin in the homeostasis of hematopoietic stem and progenitor cells. Furthermore, they suggest that Menin may regulate normal hematopoiesis through mechanisms that are distinct from its role in Hox gene-dependent malignant transformation.

Functional dominance among Hox genes: repression dominates activation in the regulation of Dpp

Development ◽  
1998 ◽  
Vol 125 (24) ◽  
pp. 4949-4957 ◽  
Author(s):  
M. Capovilla ◽  
J. Botas
Keyword(s):  
Gene Regulation ◽  
Target Gene ◽  
Hox Genes ◽  
Hox Gene ◽  
Visceral Mesoderm ◽  
Positional Identity ◽  
The One

Here we investigate the mechanisms by which Hox genes compete for the control of positional identity. Functional dominance is often observed where different Hox genes are co-expressed, and frequently the more posteriorly expressed Hox gene is the one that prevails, a phenomenon known as posterior prevalence. We use dpp674, a visceral mesoderm-specific enhancer of decapentaplegic (dpp), to investigate functional dominance among Hox genes molecularly. We find that posterior prevalence does not adequately describe the regulation of dpp by Hox genes. Instead, we find that abdominal-A (abd-A) dominates over the more posterior Abdominal-B (Abd-B) and the more anterior Ultrabithorax (Ubx). In the context of the dpp674 enhancer, abd-A functions as a repressor whereas Ubx and Abd-B function as activators. Thus, these results suggest that other cases of Hox competition and functional dominance may also be understood in terms of competition for target gene regulation in which repression dominates over activation.

scholarly journals The anterior Hox gene ceh-13 and elt-1/GATA activate the posterior Hox genes nob-1 and php-3 to specify posterior lineages in the C. elegans embryo

2021 ◽  
Author(s):  
John Isaac Murray ◽  
Elicia Preston ◽  
Jeremy P. Crawford ◽  
Jonathan D. Rumley ◽  
Prativa Amom ◽  
...  
Keyword(s):  
Gene Regulation ◽  
Cell Division ◽  
Hox Genes ◽  
Hox Gene ◽  
Animal Development ◽  
C Elegans ◽  
Transcriptional Enhancers ◽  
Positional Identity ◽  
Cell Position ◽  
And Function

AbstractHox transcription factors play a conserved role in specifying positional identity during animal development, with posterior Hox genes typically repressing the expression of more anterior Hox genes. Here, we dissect the regulation of the posterior Hox genes nob-1 and php-3 in the nematode C. elegans. We show that nob-1 and php-3 are co-expressed in gastrulation-stage embryos in cells that express the anterior Hox gene ceh-13. This expression is controlled by several partially redundant transcriptional enhancers. Surprisingly, these enhancers require ceh-13 for expression, providing an example of an anterior Hox gene positively regulating a posterior Hox gene. Several other regulators also act positively through nob-1/php-3 enhancers, including elt-1/GATA, ceh-20/ceh-40/Pbx, unc-62/Meis, pop-1/TCF, ceh-36/Otx and unc-30/Pitx. We identified defects in both cell position and cell division patterns in ceh-13 and nob-1;php-3 mutants, suggesting that these factors regulate lineage identity in addition to positional identity. Together, our results highlight the complexity and remarkable flexibility of Hox gene regulation and function.

scholarly journals Temporal dynamics and developmental memory of 3D chromatin architecture at Hox gene loci

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Daan Noordermeer ◽  
Marion Leleu ◽  
Patrick Schorderet ◽  
Elisabeth Joye ◽  
Fabienne Chabaud ◽  
...  
Keyword(s):  
Transcriptional Activation ◽  
Hox Genes ◽  
Temporal Dynamics ◽  
Gene Products ◽  
Circular Chromosome ◽  
Chromosome Conformation ◽  
Hox Gene ◽  
Circular Chromosome Conformation Capture ◽  
Hox Clusters

Hox genes are essential regulators of embryonic development. Their step-wise transcriptional activation follows their genomic topology and the various states of activation are subsequently memorized into domains of progressively overlapping gene products. We have analyzed the 3D chromatin organization of Hox clusters during their early activation in vivo, using high-resolution circular chromosome conformation capture. Initially, Hox clusters are organized as single chromatin compartments containing all genes and bivalent chromatin marks. Transcriptional activation is associated with a dynamic bi-modal 3D organization, whereby the genes switch autonomously from an inactive to an active compartment. These local 3D dynamics occur within a framework of constitutive interactions within the surrounding Topological Associated Domains, indicating that this regulation process is mostly cluster intrinsic. The step-wise progression in time is fixed at various body levels and thus can account for the chromatin architectures previously described at a later stage for different anterior to posterior levels.

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