Binding affinities and cooperative interactions with bHLH activators delimit threshold responses to the dorsal gradient morphogen

The dorsal (dl) morphogen gradient initiates the formation of the mesoderm, neuroectoderm, and dorsal ectoderm by setting different limits of regulatory gene expression along the dorsoventral axis of the early Drosophila embryo. In this paper, we show that low affinity dl-binding sites restrict target gene expression to the ventralmost regions (presumptive mesoderm), where there are peak levels of dl, while high affinity sites permit expression in ventrolateral regions (mesoderm and mesectoderm) containing intermediate levels of the morphogen. Activation by low levels of dl in lateral regions (the presumptive neuroectoderm) depends on cooperative DNA binding interactions between dl and bHLH proteins. The snail repressor blocks this interaction and restricts expression to the neuroectoderm. We discuss how enhancers serve as templates to bring weakly interacting regulatory factors into close proximity so that they can function combinatorially to activate and repress transcription.

[1]  M. Levine,et al.  Regulation of a segmentation stripe by overlapping activators and repressors in the Drosophila embryo. , 1991, Science.

[2]  B. Thisse,et al.  Genes of the Drosophila maternal dorsal group control the specific expression of the zygotic gene twist in presumptive mesodermal cells , 1987 .

[3]  G. Nolan,et al.  Cloning of the p50 DNA binding subunit of NF-κB: Homology to rel and dorsal , 1990, Cell.

[4]  K. Struhl,et al.  The gradient morphogen bicoid is a concentration-dependent transcriptional activator , 1989, Cell.

[5]  M. Ptashne,et al.  GAL4 activates gene expression in mammalian cells , 1988, Cell.

[6]  M. Leptin.  twist and snail as positive and negative regulators during Drosophila mesoderm development. , 1991, Genes & development.

[7]  D. Melton,et al.  Pattern formation during animal development. , 1991, Science.

[8]  R. Lehmann,et al.  Determination of anteroposterior polarity in Drosophila. , 1987, Science.

[9]  D. Baltimore,et al.  Protein-binding sites in Ig gene enhancers determine transcriptional activity and inducibility. , 1987, Science.

[10]  J. Boulay,et al.  The snail gene required for mesoderm formation in Drosophila is expressed dynamically in derivatives of all three germ layers. , 1991, Development.

[11]  M. Levine,et al.  Transcriptional regulation of a pair-rule stripe in Drosophila. , 1991, Genes & development.

[12]  Y. Jan,et al.  Interactions between heterologous helix-loop-helix proteins generate complexes that bind specifically to a common DNA sequence , 1989, Cell.

[13]  J. Posakony,et al.  The Drosophila extramacrochaetae protein antagonizes sequence-specific DNA binding by daughterless/achaete-scute protein complexes. , 1991, Development.

[14]  C. Nüsslein-Volhard,et al.  The origin of pattern and polarity in the Drosophila embryo , 1992, Cell.

[15]  M. Levine,et al.  The graded distribution of the dorsal morphogen is initiated by selective nuclear transport in Drosophila , 1989, Cell.

[16]  D. Smith,et al.  Single-step purification of polypeptides expressed in Escherichia coli as fusions with glutathione S-transferase. , 1988, Gene.

[17]  M. Beato,et al.  Ubiquitous transcription factor OTF-1 mediates induction of the MMTV promoter through synergistic interaction with hormone receptors , 1991, Cell.

[18]  Wolfgang Driever,et al.  Determination of spatial domains of zygotic gene expression in the Drosophila embryo by the affinity of binding sites for the bicoid morphogen , 1989, Nature.

[19]  M. Levine,et al.  Transcriptional repression of eukaryotic promoters , 1989, Cell.

[20]  M. Levine,et al.  Autoregulation of a segmentation gene in Drosophila: combinatorial interaction of the even-skipped homeo box protein with a distal enhancer element. , 1991, Genes & development.

[21]  T. Maniatis,et al.  Identification and characterization of a novel repressor of beta-interferon gene expression. , 1991, Genes & development.

[22]  J. L. Boulay,et al.  The Drosophila developmental gene snail encodes a protein with nucleic acid binding fingers , 1987, Nature.

[23]  W. Gelbart,et al.  Decapentaplegic transcripts are localized along the dorsal‐ventral axis of the Drosophila embryo. , 1987, The EMBO journal.

[24]  J. D. Huang,et al.  Functional analysis of the Drosophila twist promoter reveals a dorsal-binding ventral activator region. , 1991, Genes & development.

[25]  K. Sander.  Pattern specification in the insect embryo. , 2008, Ciba Foundation symposium.

[26]  R. Steward.  Dorsal, an embryonic polarity gene in Drosophila, is homologous to the vertebrate proto-oncogene, c-rel. , 1987, Science.

[27]  R. Steward.  Relocalization of the dorsal protein from the cytoplasm to the nucleus correlates with its function , 1989, Cell.

[28]  Y. Jan,et al.  rhomboid, a gene required for dorsoventral axis establishment and peripheral nervous system development in Drosophila melanogaster. , 1990, Genes & development.

[29]  A. Courey,et al.  The same dorsal binding site mediates both activation and repression in a context‐dependent manner. , 1992, The EMBO journal.

[30]  T. Cline,et al.  Molecular nature of the Drosophila sex determination signal and its link to neurogenesis. , 1991, Science.

[31]  C. Nüsslein-Volhard,et al.  A gradient of nuclear localization of the dorsal protein determines dorsoventral pattern in the Drosophila embryo , 1989, Cell.

[32]  B. Thisse,et al.  Sequence-specific transactivation of the Drosophila twist gene by the dorsal gene product , 1991, Cell.

[33]  M. Frasch,et al.  Maternal regulation of zerknüllt: a homoeobox gene controlling differentiation of dorsal tissues in Drosophila , 1987, Nature.

[34]  Michael Carey,et al.  How different eukaryotic transcriptional activators can cooperate promiscuously , 1990, Nature.

[35]  Harold Weintraub,et al.  The protein Id: A negative regulator of helix-loop-helix DNA binding proteins , 1990, Cell.

[36]  M. Levine,et al.  The dorsal gradient morphogen regulates stripes of rhomboid expression in the presumptive neuroectoderm of the Drosophila embryo. , 1992, Genes & development.

[37]  Peter A. Lawrence,et al.  Control of Drosophila body pattern by the hunchback morphogen gradient , 1992, Cell.

[38]  M. Levine,et al.  Regulation of even‐skipped stripe 2 in the Drosophila embryo. , 1992, The EMBO journal.

[39]  Michael Carey,et al.  A mechanism for synergistic activation of a mammalian gene by GAL4 derivatives , 1990, Nature.

[40]  Y. Jan,et al.  Neuroectoderm in Drosophila embryos is dependent on the mesoderm for positioning but not for formation. , 1991, Genes & development.

[41]  P. Lieberman,et al.  Dorsal-ventral patterning in Drosophila: DNA binding of snail protein to the single-minded gene. , 1992, Proceedings of the National Academy of Sciences of the United States of America.

[42]  M. Levine,et al.  Synergistic activation and repression of transcription by Drosophila homeobox proteins , 1989, Cell.

[43]  M. Levine,et al.  Spatial regulation of zerknüllt: a dorsal-ventral patterning gene in Drosophila. , 1989, Genes & development.

[44]  P. Simpson,et al.  Maternal-Zygotic Gene Interactions during Formation of the Dorsoventral Pattern in Drosophila Embryos. , 1983, Genetics.

[45]  D Kosman,et al.  The dorsal morphogen gradient regulates the mesoderm determinant twist in early Drosophila embryos. , 1991, Genes & development.

[46]  M. Levine,et al.  The dorsal morphogen is a sequence-specific DNA-binding protein that interacts with a long-range repression element in drosophila , 1991, Cell.

[47]  D Kosman,et al.  Establishment of the mesoderm-neuroectoderm boundary in the Drosophila embryo. , 1991, Science.

[48]  A. Israël,et al.  The DNA binding subunit of NF-κB is identical to factor KBF1 and homologous to the rel oncogene product , 1990, Cell.

[49]  M. Levine,et al.  Individual dorsal morphogen binding sites mediate activation and repression in the Drosophila embryo. , 1992, The EMBO journal.

[50]  G. Rubin,et al.  Genetic transformation of Drosophila with transposable element vectors. , 1982, Science.

[51]  J. Smith,et al.  Growth factors as morphogens: do gradients and thresholds establish body plan? , 1991, Trends in genetics : TIG.

[52]  Stephen T. Crews,et al.  The Drosophila single-minded gene encodes a nuclear protein with sequence similarity to the per gene product , 1988, Cell.

[53]  C. Thummel,et al.  Vectors for Drosophila P-element-mediated transformation and tissue culture transfection. , 1988, Gene.