Biochemical and biophysical research communications
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Biochem. Biophys. Res. Commun. · Jul 2004
Transcriptional regulation of the TGF-beta pseudoreceptor BAMBI by TGF-beta signaling.
BAMBI is a transmembrane glycoprotein related to the transforming growth factor-beta (TGF-beta)-family type I receptors and functions as a negative regulator of TGF-beta signaling during development. BAMBI is induced by BMP signaling through the evolutionary conserved BMP-responsive elements in its promoter. ⋯ Here, we show that BAMBI is also directly induced by TGF-beta signaling, through the three tandem repeats of 13 bp sequences containing the SMAD-binding elements, which are distinct from the BMP-responsive element. Our findings suggest that BAMBI transcription is regulated by TGF-beta signaling through direct binding of SMAD3 and SMAD4 to the BAMBI promoter.
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Biochem. Biophys. Res. Commun. · Jul 2004
Fusion of Aequorea victoria GFP and aequorin provides their Ca(2+)-induced interaction that results in red shift of GFP absorption and efficient bioluminescence energy transfer.
The bioluminescence emitted by Aequorea victoria jellyfish is greenish while its single bioluminescent photoprotein aequorin emits blue light. This phenomenon may be explained by a bioluminescence resonance energy transfer (BRET) from aequorin chromophore to green fluorescent protein (GFP) co-localized with it. However, a slight overlapping of the aequorin bioluminescence spectrum with the GFP absorption spectrum and the absence of marked interaction between these proteins in vitro pose a question on the mechanism providing the efficient BRET in A. victoria. ⋯ First, it is the presence of Ca(2+)-induced interaction between the donor and acceptor in the aequorin-containing fusion and the absence of the interaction in the obelin-containing fusion. Second, it is a red shift of GFP absorption toward better overlapping with aequorin bioluminescence induced by the interaction of aequorin with GFP. Since the connection of the two proteins in vitro mimics their proximity in vivo, Ca(2+)-induced interaction between aequorin and GFP may occur in A. victoria jellyfish providing efficient BRET in this organism.