Repression through a distal TCF-3 binding site restricts Xenopus myf-5 expression in gastrula mesoderm.
The development of skeletal muscle in the vertebrate embryo is controlled by a transcriptional cascade that includes the four myogenic regulatory factors Myf-5, MyoD, Myogenin, and MRF4. The dynamic expression pattern of myf-5 during myogenesis is thought to be consistent with its role during early determination of the myogenic lineage. To study the factors and mechanisms, which regulate myf-5 transcription in Xenopus, we isolated a genomic DNA clone containing 4858 bp of Xmyf-5 5' flanking region. Using a transgenic reporter assay, we show here that this genomic contig is sufficient to recapitulate the dynamic stage- and tissue-specific expression pattern of Xmyf-5 from the gastrula to tail bud stages. For the primary induction of myf-5 transcription, we identify three main regulatory elements, which are responsible for (i) activation in dorsal mesoderm, (ii) activation in ventral mesoderm, and (iii) repression in midline mesoderm, respectively. Their combined activities define the two-winged expression domain of myf-5 in the preinvoluted mesoderm. Repression in midline mesoderm is mediated by a single TCF binding site located in the 5' end of the -4.8 kbp sequence, which binds XTcf-3 protein in vitro. Endogenous Wnt signaling in the lateral mesoderm is required to overcome the long-range repression through this distal TCF site, and to stimulate myf-5 transcription independently from it. The element for ventral mesoderm activation responds to Activin. Together, these results describe a regulatory mosaic of repression and activation, which defines the myf-5 expression profile in the frog gastrula.
Yang
Jing
J
Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, PR China.
Mei
Wenyan
W
Otto
Andreas
A
Xiao
Lei
L
Tao
Qinghua
Q
Geng
Xin
X
Rupp
Ralph A W
RA
Ding
Xiaoyan
X
D028341:Activins / Q000378:metabolism; D000818:Animals; D030801:Animals, Genetically Modified; D001665:Binding Sites; D016384:Consensus Sequence; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D051157:Frizzled Receptors; D005775:Gastrula / Q000502:physiology*; D015870:Gene Expression; D017930:Genes, Reporter; D049452:Green Fluorescent Proteins; D024002:HMGB Proteins / Q000235:genetics / Q000378:metabolism*; D008164:Luminescent Proteins / Q000235:genetics; D051821:Lymphoid Enhancer-Binding Factor 1; D008648:Mesoderm / Q000502:physiology*; D009124:Muscle Proteins / Q000235:genetics*; D051787:Myogenic Regulatory Factor 5; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D012045:Regulatory Sequences, Nucleic Acid; D015398:Signal Transduction; D051820:TCF Transcription Factors; D015534:Trans-Activators; D058127:Transcription Factor 3; D058125:Transcription Factor 7-Like 1 Protein; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D051153:Wnt Proteins; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000196:embryology / Q000235:genetics / Q000378:metabolism; D029961:Zebrafish Proteins
D004268:DNA-Binding Proteins; D051157:Frizzled Receptors; D024002:HMGB Proteins; D008164:Luminescent Proteins; D051821:Lymphoid Enhancer-Binding Factor 1; D009124:Muscle Proteins; C497419:Myf5 protein, Xenopus; D051787:Myogenic Regulatory Factor 5; D011506:Proteins; D011518:Proto-Oncogene Proteins; D051820:TCF Transcription Factors; C544917:Tcf3 protein, Xenopus; D015534:Trans-Activators; D058127:Transcription Factor 3; D058125:Transcription Factor 7-Like 1 Protein; D014157:Transcription Factors; D051153:Wnt Proteins; D029867:Xenopus Proteins; D029961:Zebrafish Proteins; D028341:Activins; D049452:Green Fluorescent Proteins