Transcriptional regulation of the Xlim-1 gene by activin is mediated by an element in intron I.
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.
Rebbert
M L
ML
Laboratory of Molecular Genetics, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
Dawid
I B
IB
D028341:Activins; D000818:Animals; D001483:Base Sequence; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics*; D007265:Inhibins / Q000235:genetics*; D007438:Introns / Q000235:genetics; D060850:LIM-Homeodomain Proteins; D008969:Molecular Sequence Data; D014157:Transcription Factors; D014158:Transcription, Genetic; D014981:Xenopus; D029867:Xenopus Proteins
D018398:Homeodomain Proteins; D060850:LIM-Homeodomain Proteins; C543964:Lhx1 protein, Xenopus; D014157:Transcription Factors; D029867:Xenopus Proteins; D028341:Activins; D007265:Inhibins