The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
Sarah E. Bondos - One of the best experts on this subject based on the ideXlab platform.
-
Functionalization of Ultrabithorax Materials with Vascular Endothelial Growth Factor Enhances Angiogenic Activity.
Biomacromolecules, 2016Co-Authors: David W. Howell, Sarah E. Bondos, Camille L. Duran, Shang-pu Tsai, Kayla J. BaylessAbstract:Successful design of tissue engineering scaffolds must include the ability to stimulate vascular development by incorporating angiogenic growth factors. Current approaches can allow diffusion of growth factors, incorporate active factors randomly, or can leave residual toxins. We addressed these problems by genetically fusing the gene encoding Vascular Endothelial Growth Factor (VEGF) with the Ultrabithorax (Ubx) gene to produce fusion proteins capable of self-assembly into materials. We demonstrate that VEGF-Ubx materials enhance human endothelial cell migration, prolong cell survival, and dose-dependently activate the VEGF signaling pathway. VEGF-Ubx fibers attract outgrowing sprouts in an aortic ring assay and induce vessel formation in a chicken embryo chorioallantoic membrane (CAM) assay. Collectively, these results demonstrate that the activity of VEGF remains intact in Ubx materials. This approach could provide an inexpensive and facile mechanism to stimulate and pattern angiogenesis.
-
Functionalization of Ultrabithorax Materials with Vascular Endothelial Growth Factor Enhances Angiogenic Activity
2016Co-Authors: David W. Howell, Sarah E. Bondos, Camille L. Duran, Shang-pu Tsai, Kayla J. BaylessAbstract:Successful design of tissue engineering scaffolds must include the ability to stimulate vascular development by incorporating angiogenic growth factors. Current approaches can allow diffusion of growth factors, incorporate active factors randomly, or can leave residual toxins. We addressed these problems by genetically fusing the gene encoding Vascular Endothelial Growth Factor (VEGF) with the Ultrabithorax (Ubx) gene to produce fusion proteins capable of self-assembly into materials. We demonstrate that VEGF-Ubx materials enhance human endothelial cell migration, prolong cell survival, and dose-dependently activate the VEGF signaling pathway. VEGF-Ubx fibers attract outgrowing sprouts in an aortic ring assay and induce vessel formation in a chicken embryo chorioallantoic membrane (CAM) assay. Collectively, these results demonstrate that the activity of VEGF remains intact in Ubx materials. This approach could provide an inexpensive and facile mechanism to stimulate and pattern angiogenesis
-
Culture of Tumorigenic Cells on Protein Fibers Reveals Metastatic Cell Behaviors
2016Co-Authors: Hao-ching Hsiao, David W. Howell, Andres Santos, Jan L. Patterson, Robin S.l. Fuchs-young, Sarah E. BondosAbstract:Tumorigenic cell behaviors can be suppressed or enhanced by their physicochemical environment. As a first step toward developing materials that allow tumorigenic behaviors to be observed and manipulated, we cultured related MCF10 breast cell lines on fibers composed of the Drosophila protein Ultrabithorax (Ubx). These cell lines, originally derived from fibrocystic breast tissue, represent a continuum of tumorigenic behavior. Immortal but nontumorigenic MCF10A cells, as well as semitumorigenic MCF10AT cells, attached and spread on Ubx fibers. MCF10CA-1a cells, the most highly transformed line, secreted high concentrations of matrix metalloproteinases when cultured on Ubx materials, resulting in differences in cell attachment and cytoskeletal structure, and enabling invasive behavior. Because the mechanical and functional properties of Ubx fibers can be genetically manipulated, these materials provide a valuable tool for cancer research, allowing creation of diverse microenvironments that allow assessment of invasive, metastatic behavior
-
Physical and Genetic Interactions Link Hox Function with Diverse Transcription Factors and Cell
2015Co-Authors: Signaling Proteins, Sarah E. Bondos, Xin-xing Tan, Kathleen S. MatthewsAbstract:scription factors is integrated with other transcription fac-tors and cell signaling cascades in specific combinations to dictate context- and gene-specific Hox activity. Pro-tein-protein interactions between these groups have long been hypothesized to modulate Hox functions, yielding a context-specific function. However, difficulties in applying interaction screens to potent transcription factors have limited partner identification. A yeast two-hybrid screen using transcription activation-deficient mutants of the Drosophila melanogaster Hox protein Ultrabithorax IB identified an array of interacting proteins, consisting pri-marily of transcription factors and components of cell signaling pathways. Interactions were confirmed with wild-type Ultrabithorax (UBX) in phage display experi-ments and by immunoprecipitation for a subset of part
-
materials composed of the drosophila melanogaster protein Ultrabithorax are cytocompatible
Journal of Biomedical Materials Research Part A, 2014Co-Authors: Jan Patterson, Sarah E. Bondos, Colette A. Abbey, Kayla J. BaylessAbstract:The Drosophila melanogaster Hox protein Ultrabithorax (Ubx) has the interesting ability to hierarchically self-assemble in vitro into materials that have mechanical properties comparable to natural elastin. Ubx materials can be easily functionalized by gene fusion, generating potentially useful scaffolds for cell and tissue engineering. Here, we tested the cytocompatibility of fibers composed of Ubx or an mCherry-Ubx fusion protein. Fibers were cultured with three primary human cell lines derived from vasculature at low passage: umbilical vein endothelial cells, brain vascular pericytes, or aortic smooth muscle cells. No direct or indirect toxicity was observed for any cell line, in response to fibers composed of either plain Ubx or mCherry-Ubx. Cells readily adhered to Ubx fibers, and cells attached to fibers could be transferred between tissue cultures without loss of viability for at least 96 h. When attached to fibers, the morphology of the three cell lines differed somewhat, but all cells in contact with Ubx fibers exhibited a microtubular network aligned with the long axis of Ubx fibers. Thus, Ubx fibers are cytocompatible with cultured primary human vascular cells. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 102A: 97–104, 2014.
Kathleen S. Matthews - One of the best experts on this subject based on the ideXlab platform.
-
Physical and Genetic Interactions Link Hox Function with Diverse Transcription Factors and Cell
2015Co-Authors: Signaling Proteins, Sarah E. Bondos, Xin-xing Tan, Kathleen S. MatthewsAbstract:scription factors is integrated with other transcription fac-tors and cell signaling cascades in specific combinations to dictate context- and gene-specific Hox activity. Pro-tein-protein interactions between these groups have long been hypothesized to modulate Hox functions, yielding a context-specific function. However, difficulties in applying interaction screens to potent transcription factors have limited partner identification. A yeast two-hybrid screen using transcription activation-deficient mutants of the Drosophila melanogaster Hox protein Ultrabithorax IB identified an array of interacting proteins, consisting pri-marily of transcription factors and components of cell signaling pathways. Interactions were confirmed with wild-type Ultrabithorax (UBX) in phage display experi-ments and by immunoprecipitation for a subset of part
-
Ultrabithorax, an Intrinsically Disordered Protein, Selects Protein Interactions by Topology
Biophysical Journal, 2012Co-Authors: Sarah E. Bondos, Hao-ching Hsiao, Daniel J. Catanese, Kristopher E. Jordy, Kathleen S. MatthewsAbstract:Interaction between two structured proteins requires both complementary topologies to generate a sufficient interface and surface groups capable of forming bonds within this interface to stabilize the complex. When one (or both) partners is intrinsically disordered as a monomer, but folds upon interaction, the same rules for partner selection - complementary topology and surface chemistry - are expected to apply. However, many proteins do not fold even when forming stable protein interactions, creating “fuzzy” protein complexes. In these cases, the extreme instability of one partner may preclude forming a well-defined interface. Despite the apparent lack of constraints, these proteins specifically and reliably select the correct protein partners in vivo. To understand the rules that determine partner selection when forming fuzzy complexes, we have evaluated protein interactions formed by the Drosophila melanogaster Hox transcription factor Ultrabithorax (Ubx). Ubx interacts in vitro with 29 other proteins. All of these interactions require the intrinsically disordered regions within Ubx. Surprisingly, despite the extreme lack of structure within these regions, Ubx appears to select protein interactions by topology: 22 of the 29 partners include one of five protein folds out of the nearly 1200 folds listed in SCOP. These data suggest that topology remains a constraint even in fuzzy complexes. Although some Ubx partners bind equally well to both large intrinsically disordered regions within Ubx, many partners clearly prefer binding to the disordered alternatively spliced microexons. Partners preferring the microexon region bind various Ubx splicing isoforms differentially. Consequently, surface chemistry is likely important for these interactions. Together, our data suggests that both topology and surface chemistry are key criteria for partner selection, even in fuzzy complexes.
-
functionalization and patterning of protein based materials using active Ultrabithorax chimeras
Advanced Functional Materials, 2011Co-Authors: Zhao Huang, Kathleen S. Matthews, Jan Patterson, Taha Salim, Autumn Brawley, Sarah E. BondosAbstract:A key advantage of protein-based materials is the potential to directly incorporate novel functions via gene fusion to produce a single chimeric polypeptide capable of both self-assembly and the desired activity. However, facile production of functionalized protein materials is frequently hampered by the need to trigger materials assembly using conditions that will not irreversibly damage the functional protein. In contrast, the recombinant Drosophila melanogaster transcription factor Ultrabithorax (Ubx) rapidly self-assembles under mild, aqueous conditions to form highly extensible materials with a variety of morphologies. Here, it is demonstrated that materials composed of Ubx chimeras with Enhanced Green Fluorescent Protein (EGFP), mCherry, luciferase, or myoglobin display the functions of the appended proteins, indicating that these activities are neither impaired by the assembly process nor by confinement within the materials. Finally, methods are established that combine EGFP-Ubx and mCherry-Ubx monomers to self-assemble materials patterned on the microscale to macroscale. The self-adhesive properties of Ubx materials also permit manual construction and patterning of more complex forms. The ability to easily functionalize and pattern protein-based materials greatly expands their potential utility in a wide variety of applications.
-
Size dictates mechanical properties for protein fibers self-assembled by the Drosophila hox transcription factor Ultrabithorax.
Biomacromolecules, 2010Co-Authors: Zhao Huang, Kathleen S. Matthews, Sarah E. Bondos, Ravish Majithia, Jaimin S. Shah, Kenith E. Meissner, Jun LouAbstract:The development of protein-based materials with diverse mechanical properties will facilitate the realization of a broad range of potential applications. The recombinant Drosophila melanogaster transcription factor Ultrabithorax self-assembles under mild conditions in aqueous buffers into extremely extensible materials. By controlling fiber diameter, both the mechanism of extension and the magnitude of the mechanical properties can be varied. Narrow Ultrabithorax fibers (diameter 15 μm) reflects the increase in breaking strain with increasing diameter, apparently due to a change in structure. The breaking stress/strain of the widest fibers resembles that of natural elastin. Intermediate fibers display mixed properties. Fiber bundles retain the mechanical properties of individual fibers but can withstand much larger forces. Controlling fiber size and generating fiber superstructures is a facile way to manipulate the mechanical characteristics of protein fibers and rationally engineer macroscale protein-based materials with desirable properties.
-
The Drosophila transcription factor Ultrabithorax self-assembles into protein-based biomaterials with multiple morphologies.
Biomacromolecules, 2009Co-Authors: Alexandra M. Greer, Zhao Huang, Ashley Oriakhi, Jun Lou, Kathleen S. Matthews, Sarah E. BondosAbstract:The use of proteins as monomers for materials assembly enables customization of chemical, physical, and functional properties. However, natural materials-forming proteins are difficult to produce as recombinant protein monomers and require harsh conditions to initiate assembly. We have generated materials using the recombinant transcription factor Ultrabithorax, a Drosophila melanogaster protein not known or anticipated to form extended oligomers in vivo. Ultrabithorax self-assembles at the air-water interface into nanoscale fibers, which further associate to form macroscale films, sheets, ropes, and tethered encapsulates. These materials self-adhere, allowing construction of more complex architectures. The Ultrabithorax sequence contains two regions capable of generating materials, only one of which contains motifs found in elastomeric proteins. However, both minimal regions must be included to produce robust materials. Relative to other protein-based materials, Ultrabithorax assembles at significantly reduced concentrations, on faster timescales, and under gentler conditions, properties that facilitate future materials engineering and functionalization.
Richard S. Mann - One of the best experts on this subject based on the ideXlab platform.
-
Control of tissue morphogenesis by the HOX gene Ultrabithorax.
Development (Cambridge England), 2020Co-Authors: Maria-del-carmen Diaz-de-la-loza, Richard S. Mann, Ryan Loker, Barry J. ThompsonAbstract:ABSTRACT Mutations in the Ultrabithorax (Ubx) gene cause homeotic transformation of the normally two-winged Drosophila into a four-winged mutant fly. Ubx encodes a HOX family transcription factor that specifies segment identity, including transformation of the second set of wings into rudimentary halteres. Ubx is known to control the expression of many genes that regulate tissue growth and patterning, but how it regulates tissue morphogenesis to reshape the wing into a haltere is still unclear. Here, we show that Ubx acts by repressing the expression of two genes in the haltere, Stubble and Notopleural, both of which encode transmembrane proteases that remodel the apical extracellular matrix to promote wing morphogenesis. In addition, Ubx induces expression of the Tissue inhibitor of metalloproteases in the haltere, which prevents the basal extracellular matrix remodelling necessary for wing morphogenesis. Our results provide a long-awaited explanation for how Ubx controls morphogenetic transformation.
-
Structure of a DNA-bound Ultrabithorax–Extradenticle homeodomain complex
Nature, 1999Co-Authors: Jonathan M. Passner, Hyung Don Ryoo, Leyi Shen, Richard S. Mann, Aneel K. AggarwalAbstract:During the development of multicellular organisms, gene expression must be tightly regulated, both spatially and temporally. One set of transcription factors that are important in animal development is encoded by the homeotic (Hox) genes, which govern the choice between alternative developmental pathways along the anterior-posterior axis. Hox proteins, such as Drosophila Ultrabithorax, have low DNA-binding specificity by themselves but gain affinity and specificity when they bind together with the homeoprotein Extradenticle (or Pbxl in mammals). To understand the structural basis of Hox-Extradenticle pairing, we determine here the crystal structure of an Ultrabithorax-Extradenticle-DNA complex at 2.4 A resolution, using the minimal polypeptides that form a cooperative heterodimer. The Ultrabithorax and Extradenticle homeodomains bind opposite faces of the DNA, with their DNA-recognition helices almost touching each other. However, most of the cooperative interactions arise from the YPWM amino-acid motif of Ultrabithorax-located amino-terminally to its homeodomain-which forms a reverse turn and inserts into a hydrophobic pocket on the Extradenticle homeodomain surface. Together, these protein-DNA and protein-protein interactions define the general principles by which homeotic proteins interact with Extradenticle (or Pbx1) to affect development along the anterior-posterior axis of animals.
-
structure of a dna bound Ultrabithorax extradenticle homeodomain complex
Nature, 1999Co-Authors: Jonathan M. Passner, Hyung Don Ryoo, Leyi Shen, Richard S. Mann, Aneel K. AggarwalAbstract:During the development of multicellular organisms, gene expression must be tightly regulated, both spatially and temporally. One set of transcription factors that are important in animal development is encoded by the homeotic (Hox) genes, which govern the choice between alternative developmental pathways along the anterior–posterior axis1,2. Hox proteins, such as Drosophila Ultrabithorax, have low DNA-binding specificity by themselves but gain affinity and specificity when they bind together with the homeoprotein Extradenticle (or Pbx1 in mammals)3,4. To understand the structural basis of Hox–Extradenticle pairing, we determine here the crystal structure of an Ultrabithorax–Extradenticle–DNA complex at 2.4 A resolution, using the minimal polypeptides that form a cooperative heterodimer. The Ultrabithorax and Extradenticle homeodomains bind opposite faces of the DNA, with their DNA-recognition helices almost touching each other. However, most of the cooperative interactions arise from the YPWM amino-acid motif of Ultrabithorax—located amino-terminally to its homeodomain—which forms a reverse turn and inserts into a hydrophobic pocket on the Extradenticle homeodomain surface. Together, these protein–DNA and protein–protein interactions define the general principles by which homeotic proteins interact with Extradenticle (or Pbx1) to affect development along the anterior–posterior axis of animals.
-
The DNA binding specificity of Ultrabithorax is modulated by cooperative interactions with extradenticle, another homeoprotein
Cell, 1994Co-Authors: Siu-kwong Chan, Juan Botas, Leah Jaffe, Maria Capovilla, Richard S. MannAbstract:The Ultrabithorax (Ubx) and Antennapedia (Antp) genes of Drosophila encode homeodomain proteins that have very similar DNA binding specificities in vitro but specify the development of different segmental patterns in vivo. We describe cooperative interactions between Ubx protein and a divergent homeodomain protein, extradenticle (exd), that selectively increases the affinity of Ubx, but not Antp, for a particular DNA target. We also provide evidence that Ubx and exd bind to neighboring sites on this DNA and interact directly to stabilize the DNA-bound form of Ubx. Thus, the ability of different homeotic genes to specify distinct segmental patterns may depend on cooperative interactions with proteins such as exd that selectively modulate their otherwise similar DNA binding specificities.
-
Negative autoregulation by Ultrabithorax controls the level and pattern of its expression
Development (Cambridge England), 1993Co-Authors: Kenneth D. Irvine, Juan Botas, Richard S. Mann, Sanjaya Jha, D S HognessAbstract:The Drosophila homeotic gene Ultrabithorax (Ubx) encodes transcriptional regulatory proteins (UBX) that specify thoracic and abdominal segmental identities. Ubx autoregulation was examined by manipulating UBX levels, both genetically and with an inducible transgene, and monitoring the effect of these manipulations on the expression of Ubx and Ubx-lacZ reporter genes. Positive autoregulation by Ubx is restricted to the visceral mesoderm, while in other tissues Ubx negatively autoregulates. In some cases, negative autoregulation stabilizes UBX levels, while in others it modulates the spatial and temporal patterns of UBX expression. This modulation of UBX expression may enable Ubx to specify distinct identities in different segments. The upstream control region of Ubx contains multiple autoregulatory elements for both positive and negative autoregulation.
Ernesto Sánchez-herrero - One of the best experts on this subject based on the ideXlab platform.
-
Quantification of Mmp1 and Vkg.pdf
2018Co-Authors: José Manuel De Las Heras, Celia García-cortés, David Foronda, José Carlos Pastor-pareja, L. S. Shashidhara, Ernesto Sánchez-herreroAbstract:Macros for the quantification of Metalloproteinase 1 and Viking in wing and haltere discs of wildtype, Haltere mimic and Ultrabithorax RNAi Drosophila prepupae
-
Polycomb-dependent Ultrabithorax Hox gene silencing induced by high Ultrabithorax levels in Drosophila
Development (Cambridge England), 2008Co-Authors: Daniel L. Garaulet, David Foronda, Manuel Calleja, Ernesto Sánchez-herreroAbstract:The Ultrabithorax (Ubx) gene of Drosophila specifies the third thoracic and first abdominal segments. Ubx expression is controlled by several mechanisms, including negative regulation by its own product. We show here that if Ubx expression levels are inappropriately elevated, overriding the auto-regulatory control, a permanent repression of Ubx is established. This continuous repression becomes independent of the presence of exogenous Ubx and leads to the paradoxical result that an excess of Ubx results in a phenotype of Ubx loss. The mechanism of permanent repression depends on Polycomb-group genes. Absence of endogenous Ubx transcription when Ubx levels are highly elevated probably activates Polycomb complexes on a Polycomb response element located in the Ubx major intron. This, in turn, brings about permanent repression of Ubx transcription. Similar results are obtained with the gene engrailed, showing that this mechanism of permanent repression may be a general one for genes with negative auto-regulation when levels of expression are transitorily elevated.
-
The Ultrabithorax Hox gene of Drosophila controls haltere size by regulating the Dpp pathway.
Development (Cambridge England), 2006Co-Authors: Luis F. De ,navas, Daniel L. Garaulet, Ernesto Sánchez-herreroAbstract:The halteres and wings of Drosophila are homologous thoracic appendages, which share common positional information provided by signaling pathways. The activity in the haltere discs of the Ultrabithorax ( Ubx ) Hox gene establishes the differences between these structures, their different size being an obvious one. We show here that Ubx regulates the activity of the Decapentaplegic (Dpp) signaling pathway at different levels, and that this regulation is instrumental in establishing the size difference. Ubx downregulates dpp transcription and reduces Dpp diffusion by repressing the expression of master of thick veins and division abnormally delayed and by increasing the levels of thick veins , one of the Dpp receptors. Our results suggest that modulation in Dpp expression and spread accounts, in part, for the different size of halteres and wings.
-
Interactions of Drosophila Ultrabithorax regulatory regions with native and foreign promoters.
Genetics, 1997Co-Authors: Fernando Casares, Welcome Bender, John R. Merriam, Ernesto Sánchez-herreroAbstract:The Ultrabithorax (Ubx) gene of the Drosophila bithorax complex is required to specify parasegments 5 and 6. Two P-element "enhancer traps" have been recovered within the locus that contain the bacterial lacZ gene under the control of the P-element promoter. The P insertion that is closer to the Ubx promoter expresses lacZ in a pattern similar to that of the normal Ubx gene, but also in parasegment 4 during embryonic development. Two deletions have been recovered that remove the normal Ubx promoter plus several kilobases on either side, but retain the lacZ reporter gene. The lacZ patterns from the deletion derivatives closely match the normal pattern of Ubx expression in late embryos and imaginal discs. The lacZ genes in the deletion derivatives are also negatively regulated by Ubx and activated in trans by Contrabithorax mutations, again like the normal Ubx gene. Thus, the deleted regions, including several kilobases around the Ubx promoter, are not required for long range interactions with Ubx regulatory regions. The deletion derivatives also stimulate transvection, a pairing-dependent interaction with the Ubx promoter on the homologous chromosome.
-
FUNCTIONAL SIMILARITY IN APPENDAGE SPECIFICATION BY THE Ultrabithorax AND ABDOMINAL-A DROSOPHILA HOX GENES
The EMBO journal, 1996Co-Authors: Fernando Casares, M Calleja, Ernesto Sánchez-herreroAbstract:In Drosophila, the Ultrabithorax, abdominal-A and Abdominal-B HOX genes of the bithorax complex determine the identity of part of the thorax and the whole abdomen. Either the absence of these genes or their ectopic expression transform segments into the identity of different ones along the antero-posterior axis. Here we show that misexpression of Ultrabithorax, abdominal-A and, to some extent, Abdominal-B genes cause similar transformations in some of the fruitfly appendages: antennal tissue into leg tissue and wing tissue into haltere tissue. abdominal-A can fully, and Abdominal-B partially, substitute for Ultrabithorax in haltere development. By contrast, when ectopically expressed, the three genes specify different segments in regions of the main body axis like notum or abdomen. Insects may have originally used the HOX genes primarily to specify this main body axis. By contrast, the homeotic requirement to form appendages is, in some cases, non-specific.
Aneel K. Aggarwal - One of the best experts on this subject based on the ideXlab platform.
-
Structure of a DNA-bound Ultrabithorax–Extradenticle homeodomain complex
Nature, 1999Co-Authors: Jonathan M. Passner, Hyung Don Ryoo, Leyi Shen, Richard S. Mann, Aneel K. AggarwalAbstract:During the development of multicellular organisms, gene expression must be tightly regulated, both spatially and temporally. One set of transcription factors that are important in animal development is encoded by the homeotic (Hox) genes, which govern the choice between alternative developmental pathways along the anterior-posterior axis. Hox proteins, such as Drosophila Ultrabithorax, have low DNA-binding specificity by themselves but gain affinity and specificity when they bind together with the homeoprotein Extradenticle (or Pbxl in mammals). To understand the structural basis of Hox-Extradenticle pairing, we determine here the crystal structure of an Ultrabithorax-Extradenticle-DNA complex at 2.4 A resolution, using the minimal polypeptides that form a cooperative heterodimer. The Ultrabithorax and Extradenticle homeodomains bind opposite faces of the DNA, with their DNA-recognition helices almost touching each other. However, most of the cooperative interactions arise from the YPWM amino-acid motif of Ultrabithorax-located amino-terminally to its homeodomain-which forms a reverse turn and inserts into a hydrophobic pocket on the Extradenticle homeodomain surface. Together, these protein-DNA and protein-protein interactions define the general principles by which homeotic proteins interact with Extradenticle (or Pbx1) to affect development along the anterior-posterior axis of animals.
-
structure of a dna bound Ultrabithorax extradenticle homeodomain complex
Nature, 1999Co-Authors: Jonathan M. Passner, Hyung Don Ryoo, Leyi Shen, Richard S. Mann, Aneel K. AggarwalAbstract:During the development of multicellular organisms, gene expression must be tightly regulated, both spatially and temporally. One set of transcription factors that are important in animal development is encoded by the homeotic (Hox) genes, which govern the choice between alternative developmental pathways along the anterior–posterior axis1,2. Hox proteins, such as Drosophila Ultrabithorax, have low DNA-binding specificity by themselves but gain affinity and specificity when they bind together with the homeoprotein Extradenticle (or Pbx1 in mammals)3,4. To understand the structural basis of Hox–Extradenticle pairing, we determine here the crystal structure of an Ultrabithorax–Extradenticle–DNA complex at 2.4 A resolution, using the minimal polypeptides that form a cooperative heterodimer. The Ultrabithorax and Extradenticle homeodomains bind opposite faces of the DNA, with their DNA-recognition helices almost touching each other. However, most of the cooperative interactions arise from the YPWM amino-acid motif of Ultrabithorax—located amino-terminally to its homeodomain—which forms a reverse turn and inserts into a hydrophobic pocket on the Extradenticle homeodomain surface. Together, these protein–DNA and protein–protein interactions define the general principles by which homeotic proteins interact with Extradenticle (or Pbx1) to affect development along the anterior–posterior axis of animals.
