title: The Brakeless co-regulator can directly activate and repress transcription in early Drosophila embryos.
abstract: The Brakeless protein performs many important functions during Drosophila development, but how it controls gene expression is poorly 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 affected genes are down-regulated in brakeless mutants. We demonstrate that genomic regions in close proximity to some of these genes are occupied by Brakeless, that over-expression of Brakeless causes a reciprocal effect on expression of these genes, and that Brakeless remains an activator of the genes upon fusion to an activation domain. Together, our results show that Brakeless can both repress and activate gene expression. A yeast two-hybrid screen identified the Mediator complex subunit Med19 as interacting with an evolutionarily conserved part of Brakeless. Both down- and up-regulated Brakeless target genes are also affected in Med19-depleted embryos, but only down-regulated targets are influenced in embryos depleted of both Brakeless and Med19. Our data provide support for a Brakeless activator function that regulates transcription by interacting with Med19. We conclude that the transcriptional co-regulator Brakeless can either activate or repress transcription depending on context.
authors.affiliation: Stockholm University, Department of Molecular Biosciences, The Wenner-Gren Institute, Arrheniuslaboratories E3, Stockholm, Sweden.
authors.forename: Filip
authors.initials: F
authors.lastname: Crona
authors.affiliation: Stockholm University, Department of Molecular Biosciences, The Wenner-Gren Institute, Arrheniuslaboratories E3, Stockholm, Sweden.
authors.forename: Per-Henrik
authors.initials: PH
authors.lastname: Holmqvist
authors.affiliation: Stockholm University, Department of Molecular Biosciences, The Wenner-Gren Institute, Arrheniuslaboratories E3, Stockholm, Sweden.
authors.forename: Min
authors.initials: M
authors.lastname: Tang
authors.affiliation: Stockholm University, Department of Molecular Biosciences, The Wenner-Gren Institute, Arrheniuslaboratories E3, Stockholm, Sweden.
authors.forename: Bhumica
authors.initials: B
authors.lastname: Singla
authors.affiliation: Stockholm University, Department of Molecular Biosciences, The Wenner-Gren Institute, Arrheniuslaboratories E3, Stockholm, Sweden.
authors.forename: Helin
authors.initials: H
authors.lastname: Vakifahmetoglu-Norberg
authors.affiliation: Stockholm University, Department of Molecular Biosciences, The Wenner-Gren Institute, Arrheniuslaboratories E3, Stockholm, Sweden.
authors.forename: Katrin
authors.initials: K
authors.lastname: Fantur
authors.affiliation: Stockholm University, Department of Molecular Biosciences, The Wenner-Gren Institute, Arrheniuslaboratories E3, Stockholm, Sweden. Electronic address: mattias.mannervik@su.se.
authors.forename: Mattias
authors.initials: M
authors.lastname: Mannervik
mesh_terms: D000818:Animals; D029721:Drosophila Proteins / Q000378:metabolism / Q000502:physiology*; D004331:Drosophila melanogaster / Q000196:embryology*; D018507:Gene Expression Regulation, Developmental; D056892:Mediator Complex / Q000378:metabolism / Q000502:physiology; D009414:Nerve Growth Factors / Q000502:physiology*; D012097:Repressor Proteins / Q000502:physiology*
chemical_list: D029721:Drosophila Proteins; C471551:MED17 protein, Drosophila; D056892:Mediator Complex; D009414:Nerve Growth Factors; D012097:Repressor Proteins; C412165:sbb protein, Drosophila
keywords: Brakeless; Drosophila embryo; Master of thickveins; Mediator complex; Scribbler; Transcription; Transcriptional co-regulator