Transcriptional regulation of the Xlim-1 gene by activin is mediated by an element in intron I
- Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892
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Contributed by Igor B. Dawid
Abstract
The Xlim-1 gene is activated in the late blastula stage of Xenopus embryogenesis in the mesoderm, and its RNA product becomes concentrated in the Spemann organizer at early gastrula stage. A major regulator of early expression of Xlim-1 is activin or an activin-like signal. We report experiments aiming to identify the activin response element in the Xlim-1 gene. The 5′ flanking region of the gene contains a constitutive promoter that is not activin responsive, whereas sequences in the first intron mediate repression of basal promoter activity and stimulation by activin. An intron-derived fragment of 212 nt is the smallest element that could mediate activin responsiveness. Nodal and act-Vg1, factors with signaling properties similar to activin, also stimulated Xlim-1 reporter constructs, whereas BMP-4 did not stimulate or repress the constructs. The mechanism of activin regulation of Xlim-1 and the sequence of the response element are distinct from activin response elements of other genes studied so far.
Footnotes
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↵ * To whom reprint requests should be addressed at: Building 6B, Room 413, National Institutes of Health, Bethesda MD 20892. e-mail: idawid{at}nih.gov.
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Data deposition: The sequence reported in this paper has been deposited in the GenBank database (accession no. AF013242).
- ABBREVIATIONS:
- AR,
- activin receptor;
- ARE,
- activin response element;
- BR,
- BMP receptor;
- TGF-β,
- transforming growth factor β;
- TK,
- thymidine kinase
