1,721,031 research outputs found
Wnt signaling and the activation of myogenesis in mammals
No full textIn the amniote embryos, specification of skeletal myoblasts occurs in the paraxial mesoderm in response to a number of signaling molecules produced by neighboring tissues such as neural tube, notochord and dorsal ectoderm. Candidate molecules for this complex signaling activity include Sonic hedgehog, Wnts and Noggin as positive activators and BMP4 as a possible inhibitor, Recently, the receptors and the post-receptor pathways for Sonic hedgehog and Wnts have been characterized, and this has opened up the possibility of linking these signaling events to the activation of myogenic regulatory factor genes such as Myf5 and MyoD and functionally related genes such as Pax3, Here we focus on the role of Wnts, their putative receptors Frizzled and the soluble antagonist Frzb1 in regulating mammalian myogenesis. Although it is becoming evident that the signaling downstream of Frizzled receptors is much more complex than anticipated, it is conceivable that it may lead to transcriptional activation of Myf5 and MyoD and to initiation of myogenesis;However, the fact that both Wnts and Sonic hedgehog have a strong effect on cell proliferation and survival suggests that they may contribute to the overall process of myogenesis by a combination of these different biological activities
A Bzip Factor-Binding To The G-Box Of Light responsive Genes In A Phosphorylation-Independent Fashion
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Repression of Fgf Signaling by Sprouty1-2 Regulates Cortical Patterning in Two Distinct Regions and Times
No full textA fundamental question in developmental biology is how signaling pathways establish a transcription factor code that controls cell proliferation, regional fate and cell fate. Morphogenesis of the rostral telencephalon is controlled in part by Fgf signaling from the rostral patterning center. How Fgf signaling is regulated in the telencephalon is critical for understanding cerebral cortex formation. Here we show that mouse Sprouty1 and Sprouty2 (Spry1-2), which encode negative feedback regulators of Fgf signaling, are affecting cortical proliferation, differentiation, and the expression of genes regulating progenitor identity in the ventricular zone. In addition, Spry2 has a later function in regulating the MAPK pathway, proliferation, and gene expression in the cortex at mid-neurogenesis. Finally, we provide evidence that Coup-TFI, a transcription factor that promotes caudal fate, does so through repressing Fgf signaling, in part by promoting Spry expression
Constitutive, light-responsive and circadian clock-responsive factors compete for the different I box elements in plant light-regulated promoters
No full textThe I box is a conserved regulatory motif which is found upstream of plant genes (rbcS, cab and nia) whose transcription is regulated by light and the circadian clock. Gel retardation and UV cross-linking assays were used to resolve two different groups of I box binding factors (IBFs) in tomato nuclear extracts. Active components of the first group (IBF-1) recognize the I box of the light-responsive rbcS promoter; one factor within this group, IBF-1a, also recognizes the adjacent G box, which has been shown previously to bind a different class of plant transcription factors, the G box binding factors (GBFs). To the limit of experimental resolution, IBF-1a and GBF compete for the same nucleotides on the G box. Nevertheless, these two activities are biochemically and immunologically distinct. The relative abundance of IBF-1a shows a vast decrease in dark-adapted plants. Factors in the second group (IBF-2), recognize the I box of the nia promoter, which is regulated both by light and the circadian clock; one factor within this group, IBF-2a, also binds the I box of a second promoter showing similar regulation, the cab promoter. The IBF-2a binding sites on the cab and nia promoters show extensive homology to a circadian clock-responsive promoter element from wheat. The abundance of IBF-2a is diurnally regulated and shows a dramatic induction around the onset of the light period. Transfer of the plants in continuous darkness demonstrates that this induction is under the control of a circadian clock. These data suggest that I box binding factors may be involved in regulation of transcription by light and the circadian clock
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