Brakeless can directly activate and repress trancription in early Drosophila embryos

• The Brakeless protein performs many important functions during development in Drosophila, but how it controls gene expression is not understood. We previously showed that Brakeless can function as a transcriptional co-repressor. In this work, we perform transcriptional profiling of brakeless mutant embryos. Unexpectedly, the majority of target genes are down-regulated in brakeless mutants. We demonstrate that genomic regions in close proximity to some of the affected genes are occupied by Brakeless, that over-expression of Brakeless causes a reciprocal effect on expression of these genes, and that the activator function of Brakeless is intact when an activation domain is fused to Brakeless. By contrast, Brakeless repressor function is neutralized by the activation domain. Together, this shows that Brakeless can both repress and activate gene expression. To identify protein interactions that result in gene repression or activation, a yeast two-hybrid screen was performed. We find that the Mediator complex subunit Med19 interacts with an evolutionarily conserved part of Brakeless. Interestingly, down-regulated but not up-regulated Brakeless target genes are also affected in Med19-depleted embryos. Our data provide support for a Brakeless activator function that regulates transcription by interacting with Med19.

Ämnesord

NATURVETENSKAP  -- Biologi -- Utvecklingsbiologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Developmental Biology (hsv//eng)

Nyckelord

utvecklingsbiologi

Developmental Biology

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