A phylogenetically conserved cis-regulatory module in the Msx2 promoter is sufficient for BMP-dependent transcription in murine and Drosophila embryos.
To understand the actions of morphogens, it is crucial to determine how they elicit different transcriptional responses in different cell types. Here, we identify a BMP-responsive enhancer of Msx2, an immediate early target of bone morphogenetic protein (BMP) signaling. We show that the BMP-responsive region of Msx2 consists of a core element, required generally for BMP-dependent expression, and ancillary elements that mediate signaling in diverse developmental settings. Analysis of the core element identified two classes of functional sites: GCCG sequences related to the consensus binding site of Mad/Smad-related BMP signal transducers; and a single TTAATT sequence, matching the consensus site for Antennapedia superclass homeodomain proteins. Chromatin immunoprecipitation and mutagenesis experiments indicate that the GCCG sites are direct targets of BMP restricted Smads. Intriguingly, however, these sites are not sufficient for BMP responsiveness in mouse embryos; the TTAATT sequence is also required. DNA sequence comparisons reveal this element is highly conserved in Msx2 promoters from mammalian orders but is not detectable in other vertebrates or non-vertebrates. Despite this lack of conservation outside mammals, the Msx2 BMP-responsive element serves as an accurate readout of Dpp signaling in a distantly related bilaterian - Drosophila. Strikingly, in Drosophila embryos, as in mice, both TTAATT and GCCG sequences are required for Dpp responsiveness, showing that a common cis-regulatory apparatus can mediate the transcriptional activation of BMP-regulated genes in widely divergent bilaterians.
Department of Biochemistry and Molecular Biology, Norris Cancer Hospital, USC Keck School of Medicine, 1441 Eastlake Avenue, Los Angeles, CA 90033, USA.
Sean M
SM
Brugger
Amy E
AE
Merrill
Jesus
J
Torres-Vazquez
Nancy
N
Wu
Man-Chun
MC
Ting
Jane Y-M
JY
Cho
Sonia L
SL
Dobias
Soyun E
SE
Yi
Karen
K
Lyons
Jeffery R
JR
Bell
Kavita
K
Arora
Rahul
R
Warrior
Robert
R
Maxson
D000818:Animals; D001483:Base Sequence; D019485:Bone Morphogenetic Proteins / Q000378:metabolism*; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004330:Drosophila / Q000196:embryology / Q000235:genetics* / Q000378:metabolism; D019143:Evolution, Molecular; D018398:Homeodomain Proteins; D051379:Mice; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic
D019485:Bone Morphogenetic Proteins; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; C084119:MSX2 protein