Multiple modes of dorsal-bHLH transcriptional synergy in the Drosophila embryo (original) (raw)

Abstract

Synergistic interactions between the maternal regulatory factor dorsal (dl) and basic helix-loop-helix (bHLH) activators are essential for initiating differentiation of the mesoderm and neuroectoderm in the early Drosophila embryo. Here we present evidence that dl-bHLH interactions mediating gene expression in the neuroectoderm and mesoderm are fundamentally distinct. Close proximity of dl and bHLH binding sites is essential for the synergistic activation of gene expression in the lateral neuroectoderm, where there are diminishing levels of the dl regulatory gradient. In contrast, sharp on/off patterns of gene expression in the presumptive mesoderm do not require linkage of these sites. Analysis of minimal and synthetic promoter elements suggests that dl and bHLH activators, such as twist, might interact with different rate-limiting components of the transcription complex. These results are consistent with two distinct modes of dl-bHLH synergy: cooperative binding to DNA (requiring linkage of sites) and synergistic contact of basal transcription factors (not requiring linkage). Finally, the characterization of a 57 bp synthetic minimal stripe unit (MSU) provides evidence for a third tier of dl-bHLH synergy. Tandem copies of the MSU function as a bona fide enhancer and can mediate neuroectoderm expression in transgenic embryos even when placed 4.5 kb downstream of a test promoter. Multiple copies of the MSU function synergistically only when linked, but not when separated. We propose that this linkage requirement provides the basis for the evolution of modular promoters composed of discrete, non-overlapping enhancers.

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Selected References

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  1. Alberga A., Boulay J. L., Kempe E., Dennefeld C., Haenlin M. The snail gene required for mesoderm formation in Drosophila is expressed dynamically in derivatives of all three germ layers. Development. 1991 Apr;111(4):983–992. doi: 10.1242/dev.111.4.983. [DOI] [PubMed] [Google Scholar]
  2. Crews S. T., Thomas J. B., Goodman C. S. The Drosophila single-minded gene encodes a nuclear protein with sequence similarity to the per gene product. Cell. 1988 Jan 15;52(1):143–151. doi: 10.1016/0092-8674(88)90538-7. [DOI] [PubMed] [Google Scholar]
  3. Edgar B. A., Lehman D. A., O'Farrell P. H. Transcriptional regulation of string (cdc25): a link between developmental programming and the cell cycle. Development. 1994 Nov;120(11):3131–3143. doi: 10.1242/dev.120.11.3131. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. González-Crespo S., Levine M. Related target enhancers for dorsal and NF-kappa B signaling pathways. Science. 1994 Apr 8;264(5156):255–258. doi: 10.1126/science.8146656. [DOI] [PubMed] [Google Scholar]
  5. Goto T., Macdonald P., Maniatis T. Early and late periodic patterns of even skipped expression are controlled by distinct regulatory elements that respond to different spatial cues. Cell. 1989 May 5;57(3):413–422. doi: 10.1016/0092-8674(89)90916-1. [DOI] [PubMed] [Google Scholar]
  6. Gray S., Szymanski P., Levine M. Short-range repression permits multiple enhancers to function autonomously within a complex promoter. Genes Dev. 1994 Aug 1;8(15):1829–1838. doi: 10.1101/gad.8.15.1829. [DOI] [PubMed] [Google Scholar]
  7. Harding K., Hoey T., Warrior R., Levine M. Autoregulatory and gap gene response elements of the even-skipped promoter of Drosophila. EMBO J. 1989 Apr;8(4):1205–1212. doi: 10.1002/j.1460-2075.1989.tb03493.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Hiromi Y., Kuroiwa A., Gehring W. J. Control elements of the Drosophila segmentation gene fushi tarazu. Cell. 1985 Dec;43(3 Pt 2):603–613. doi: 10.1016/0092-8674(85)90232-6. [DOI] [PubMed] [Google Scholar]
  9. Howard K. R., Struhl G. Decoding positional information: regulation of the pair-rule gene hairy. Development. 1990 Dec;110(4):1223–1231. doi: 10.1242/dev.110.4.1223. [DOI] [PubMed] [Google Scholar]
  10. Howard K., Ingham P., Rushlow C. Region-specific alleles of the Drosophila segmentation gene hairy. Genes Dev. 1988 Aug;2(8):1037–1046. doi: 10.1101/gad.2.8.1037. [DOI] [PubMed] [Google Scholar]
  11. Ip Y. T., Park R. E., Kosman D., Bier E., Levine M. The dorsal gradient morphogen regulates stripes of rhomboid expression in the presumptive neuroectoderm of the Drosophila embryo. Genes Dev. 1992 Sep;6(9):1728–1739. doi: 10.1101/gad.6.9.1728. [DOI] [PubMed] [Google Scholar]
  12. Ip Y. T., Park R. E., Kosman D., Yazdanbakhsh K., Levine M. dorsal-twist interactions establish snail expression in the presumptive mesoderm of the Drosophila embryo. Genes Dev. 1992 Aug;6(8):1518–1530. doi: 10.1101/gad.6.8.1518. [DOI] [PubMed] [Google Scholar]
  13. Jiang J., Kosman D., Ip Y. T., Levine M. The dorsal morphogen gradient regulates the mesoderm determinant twist in early Drosophila embryos. Genes Dev. 1991 Oct;5(10):1881–1891. doi: 10.1101/gad.5.10.1881. [DOI] [PubMed] [Google Scholar]
  14. Jiang J., Levine M. Binding affinities and cooperative interactions with bHLH activators delimit threshold responses to the dorsal gradient morphogen. Cell. 1993 Mar 12;72(5):741–752. doi: 10.1016/0092-8674(93)90402-c. [DOI] [PubMed] [Google Scholar]
  15. Kosman D., Ip Y. T., Levine M., Arora K. Establishment of the mesoderm-neuroectoderm boundary in the Drosophila embryo. Science. 1991 Oct 4;254(5028):118–122. doi: 10.1126/science.1925551. [DOI] [PubMed] [Google Scholar]
  16. Leptin M. twist and snail as positive and negative regulators during Drosophila mesoderm development. Genes Dev. 1991 Sep;5(9):1568–1576. doi: 10.1101/gad.5.9.1568. [DOI] [PubMed] [Google Scholar]
  17. Murre C., McCaw P. S., Baltimore D. A new DNA binding and dimerization motif in immunoglobulin enhancer binding, daughterless, MyoD, and myc proteins. Cell. 1989 Mar 10;56(5):777–783. doi: 10.1016/0092-8674(89)90682-x. [DOI] [PubMed] [Google Scholar]
  18. Pan D. J., Huang J. D., Courey A. J. Functional analysis of the Drosophila twist promoter reveals a dorsal-binding ventral activator region. Genes Dev. 1991 Oct;5(10):1892–1901. doi: 10.1101/gad.5.10.1892. [DOI] [PubMed] [Google Scholar]
  19. Pankratz M. J., Jäckle H. Making stripes in the Drosophila embryo. Trends Genet. 1990 Sep;6(9):287–292. doi: 10.1016/0168-9525(90)90234-w. [DOI] [PubMed] [Google Scholar]
  20. Riddihough G., Ish-Horowicz D. Individual stripe regulatory elements in the Drosophila hairy promoter respond to maternal, gap, and pair-rule genes. Genes Dev. 1991 May;5(5):840–854. doi: 10.1101/gad.5.5.840. [DOI] [PubMed] [Google Scholar]
  21. Roth S., Stein D., Nüsslein-Volhard C. A gradient of nuclear localization of the dorsal protein determines dorsoventral pattern in the Drosophila embryo. Cell. 1989 Dec 22;59(6):1189–1202. doi: 10.1016/0092-8674(89)90774-5. [DOI] [PubMed] [Google Scholar]
  22. Rushlow C. A., Han K., Manley J. L., Levine M. The graded distribution of the dorsal morphogen is initiated by selective nuclear transport in Drosophila. Cell. 1989 Dec 22;59(6):1165–1177. doi: 10.1016/0092-8674(89)90772-1. [DOI] [PubMed] [Google Scholar]
  23. Saksela K., Baltimore D. Negative regulation of immunoglobulin kappa light-chain gene transcription by a short sequence homologous to the murine B1 repetitive element. Mol Cell Biol. 1993 Jun;13(6):3698–3705. doi: 10.1128/mcb.13.6.3698. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Simpson P. Maternal-Zygotic Gene Interactions during Formation of the Dorsoventral Pattern in Drosophila Embryos. Genetics. 1983 Nov;105(3):615–632. doi: 10.1093/genetics/105.3.615. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Singh M., Birshtein B. K. NF-HB (BSAP) is a repressor of the murine immunoglobulin heavy-chain 3' alpha enhancer at early stages of B-cell differentiation. Mol Cell Biol. 1993 Jun;13(6):3611–3622. doi: 10.1128/mcb.13.6.3611. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Spradling A. C., Rubin G. M. Transposition of cloned P elements into Drosophila germ line chromosomes. Science. 1982 Oct 22;218(4570):341–347. doi: 10.1126/science.6289435. [DOI] [PubMed] [Google Scholar]
  27. Steward R. Relocalization of the dorsal protein from the cytoplasm to the nucleus correlates with its function. Cell. 1989 Dec 22;59(6):1179–1188. doi: 10.1016/0092-8674(89)90773-3. [DOI] [PubMed] [Google Scholar]
  28. Tautz D., Pfeifle C. A non-radioactive in situ hybridization method for the localization of specific RNAs in Drosophila embryos reveals translational control of the segmentation gene hunchback. Chromosoma. 1989 Aug;98(2):81–85. doi: 10.1007/BF00291041. [DOI] [PubMed] [Google Scholar]
  29. Thisse B., Stoetzel C., Gorostiza-Thisse C., Perrin-Schmitt F. Sequence of the twist gene and nuclear localization of its protein in endomesodermal cells of early Drosophila embryos. EMBO J. 1988 Jul;7(7):2175–2183. doi: 10.1002/j.1460-2075.1988.tb03056.x. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Thisse C., Perrin-Schmitt F., Stoetzel C., Thisse B. Sequence-specific transactivation of the Drosophila twist gene by the dorsal gene product. Cell. 1991 Jun 28;65(7):1191–1201. doi: 10.1016/0092-8674(91)90014-p. [DOI] [PubMed] [Google Scholar]
  31. Thomas J. B., Crews S. T., Goodman C. S. Molecular genetics of the single-minded locus: a gene involved in the development of the Drosophila nervous system. Cell. 1988 Jan 15;52(1):133–141. doi: 10.1016/0092-8674(88)90537-5. [DOI] [PubMed] [Google Scholar]
  32. Tjian R., Maniatis T. Transcriptional activation: a complex puzzle with few easy pieces. Cell. 1994 Apr 8;77(1):5–8. doi: 10.1016/0092-8674(94)90227-5. [DOI] [PubMed] [Google Scholar]
  33. Wharton K. A., Jr, Crews S. T. CNS midline enhancers of the Drosophila slit and Toll genes. Mech Dev. 1993 Mar;40(3):141–154. doi: 10.1016/0925-4773(93)90072-6. [DOI] [PubMed] [Google Scholar]