First published online May 23, 2008
Development 135, 1205e (2008)
© The Company of Biologists Limited
Dpp on the brink(er)
In Drosophila, the morphogen Dpp patterns developing structures by
directly regulating the expression of its target genes, which it also
indirectly regulates by downregulating the transcription of the nuclear
repressor brinker (brk). On
p. 2183, Yao et al.
describe the intricate way in which multiple modular brk promoter
elements generate an inverse brk expression gradient in response to
the Dpp gradient. The promoter region of brk, they report, contains
multiple compact modules, each of which contains one or more binding sites for
the Schnurri/Mad/Medea (SMM) complex (which mediates the repression of some
Dpp target genes) linked to regions that activate brk transcription.
Because the SMM complex represses these activator regions in a
distance-dependent manner, each module responds autonomously to Dpp
signalling. However, unlike other modular promoters (for example, the promoter
in the segmentation gene eve), the outputs from the regulatory
modules in brk are integrated to generate the final brk
expression pattern. This unique promoter organisation, the researchers
suggest, ensures a robust and precise response to Dpp signalling.

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Related articles in Development:
- Multiple modular promoter elements drive graded brinker expression in response to the Dpp morphogen gradient
- Li-Chin Yao, Sopheap Phin, Jane Cho, Christine Rushlow, Kavita Arora, and Rahul Warrior
Development 2008 135: 2183-2192.
[Abstract]
[Full Text]