1: Dev Biol. 2003 May 15;257(2):278-91. 

Xenopus X-box binding protein 1, a leucine zipper transcription factor, is
involved in the BMP signaling pathway.

Zhao H, Cao Y, Grunz H.

Department of Zoophysiology, University of Essen, Universitatsstrasse 5, D-45117
Essen, Germany.

We describe a novel basic leucine zipper transcription factor, XXBP-1, which
interacts with BMP-4 in a positive feedback loop. It is a maternal factor and is
zygotically expressed in the dorsal blastopore lip and ventral ectoderm with the
exception of the prospective neural plate during gastrulation. Overexpression of
XXBP-1 leads to ventralization of early embryos as described for BMP-4, and
inhibits neuralization of dissociated ectoderm. Consistent with mediating BMP
signaling, we show that the ectopic expression of XXBP-1 recovers the expression
of epidermal keratin and reverses the dorsalization imposed by truncated BMP
receptor type I, indicating that it may act downstream of the BMP receptor. Its
effects can be partially mimicked by a fusion construct containing the VP16
activator domain and the XXBP-1 DNA-binding domain. In contrast, fusing the
DNA-binding domain to the even-skipped repressor domain leads to upregulation of
the neural markers NCAM and nrp-1 in animal cap assay. Taken together, the
results suggest a role for XXBP-1 in the control of neural differentiation,
possibly as an activator.

PMID: 12729558 [PubMed - indexed for MEDLINE]


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