Promoter activity of the zebrafish bhikhari retroelement requires an intact activin signaling pathway.
We have investigated mesoderm induction in zebrafish employing the zebrafish LTR-retroelement bhikhari (bik). bik elements are transcribed in all early mesendodermal cells. This expression pattern is generated by a promoter located in the U3 region of the LTR. We show that bik is activated through the activin/Vg1 signaling pathway in an immediate early fashion. This activation critically depends on a sequence motif that occurs among others also in the Xenopus Mix2 activin response element (ARE). It has been shown that the Mix2 ARE binds FAST- 1, which complexes with Smad proteins to form a multi-protein complex. We confirm that also the bik ARE can be bound by FAST-1 in vitro. In animal cap experiments we demonstrate that this binding site is required for activin-induced transcriptional activation mediated by FAST and Smad-type proteins.
Biozentrum der Universität, Klingelbergstrasse 70, CH-4056, Basel, Switzerland.
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D028341:Activins; D000818:Animals; D004627:Embryonic Induction / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D007265:Inhibins / Q000235:genetics*; D008648:Mesoderm; D011401:Promoter Regions, Genetic; D018626:Retroelements / Q000235:genetics*; D015027:Zebrafish / Q000196:embryology* / Q000235:genetics
D018626:Retroelements; D028341:Activins; D007265:Inhibins