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The gradient morphogen bicoid is a concentration-dependent transcriptional activator
G Struhl1, K Struhl, P M Macdonald
1Howard Hughes Medical Institute, Columbia University College of Physicians and Surgeons, New York, New York 10032.
Cell
|June 30, 1989
Summary
The bicoid (bcd) protein gradient controls hunchback (hb) gene activation in Drosophila embryos. Multiple hb gene elements respond to bcd concentration, dictating precise gene expression patterns.
Area of Science:
- Developmental Biology
- Genetics
- Molecular Biology
Background:
- The bicoid (bcd) protein forms an anteroposterior gradient in early Drosophila embryos.
- bcd regulates the zygotic activation of the segmentation gene hunchback (hb) in a specific anterior domain.
Purpose of the Study:
- To investigate how the hunchback (hb) gene responds to the bicoid (bcd) protein gradient.
- To determine the role of multiple regulatory elements in mediating bcd-dependent transcription.
- To explore the concentration-dependent interaction between bcd and hb gene regulation.
Main Methods:
- Analysis of regulatory elements within the hb gene.
- In vivo expression pattern studies in Drosophila embryos.
- In vitro transcriptional activation assays in yeast.
Main Results:
- The hb gene possesses multiple regulatory elements activated by bcd protein.
- Expression patterns are critically dependent on the bcd gradient profile and hb element characteristics.
- bcd-dependent activation of hb elements occurs in yeast, requiring specific bcd protein domains.
Conclusions:
- bcd protein binds and activates the hb gene in a concentration-dependent manner.
- The bcd gradient instructs hb gene activation, defining anterior expression boundaries.
- This mechanism likely extends to other genes, with bcd activating subordinate genes based on binding affinity.
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