The role of Bicoid cooperative binding in the patterning of sharp borders in Drosophila melanogaster
| Autor: | Paulo Mascarello Bisch, Alexander V. Spirov, Francisco J. P. Lopes |
|---|---|
| Rok vydání: | 2012 |
| Předmět: |
Embryo
Nonmammalian animal structures Hill coefficient DNA-binding protein Article 03 medical and health sciences 0302 clinical medicine Animals Drosophila Proteins Genes Developmental Bicoid Gene Transcription factor Molecular Biology Body Patterning 030304 developmental biology Homeodomain Proteins Genetics 0303 health sciences biology Hunchback Cooperative binding Drosophila embryogenesis Embryo Cell Biology biology.organism_classification Cell biology DNA-Binding Proteins Drosophila melanogaster embryonic structures Trans-Activators Self-regulation 030217 neurology & neurosurgery Drosophila Protein Transcription Factors Developmental Biology |
| Zdroj: | Developmental Biology. 370(2):165-172 |
| ISSN: | 0012-1606 |
| DOI: | 10.1016/j.ydbio.2012.07.020 |
| Popis: | In Drosophila embryonic development, the Bicoid (Bcd) protein establishes positional information of downstream developmental genes like hunchback (hb), which has a strong anterior expression and a sharp on-off boundary in the mid-embryo. The role of Bcd cooperative binding in the positioning of the Hb pattern has been previously demonstrated. However, there are discrepancies in the reported results about the role of this mechanism in the sharp Hb border. Here, we determined the Hill coefficient (nH) required for Bcd to generate the sharp border of Hb in wild-type (WT) embryos. We found that an nH of approximately 6.3 (s.d. 1.4) and 10.8 (s.d. 4.0) is required to account for Hb sharpness at early and late cycle 14A, respectively. Additional mechanisms are possibly required because the high nH is likely unachievable for Bcd binding to the hb promoter. To test this idea, we determined the nH required to pattern the Hb profile of 15 embryos expressing an hb14F allele that is defective in self-activation and found nH to be 3.0 (s.d. 1.0). This result indicates that in WT embryos, the hb self-activation is important for Hb sharpness. Corroborating our results, we also found a progressive increase in the required value of nH spanning from 4.0 to 9.2 by determining this coefficient from averaged profiles of eight temporal classes at cycle 14A (T1 to T8). Our results indicate that there is a transition in the mechanisms responsible for the sharp Hb border during cycle 14A: in early stages of this cycle, Bcd cooperative binding is primarily responsible for Hb sharpness; in late cycle 14A, hb self-activation becomes the dominant mechanism. |
| Databáze: | OpenAIRE |
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