Xenbase Image ID: 147898

A model for the role of XRnf12 in the establishment of proper Xlim-1/Ldb1 stoichiometry in the Spemann organizer. In the organizer, tetramer formation of Xlim-1/Ldb1 is required for their activity. XRnf12 selectively degrades excess Ldb1 unbound to Xlim-1, which interferes with organizer gene expression presumably by disturbing Xlim-1/Ldb1 tetramer formation. Excess Ldb1 may also possibly interfere with LIM domain-dependent association of Xlim-1 with other proteins. In this way, proper stoichiometry and maximal activity of Xlim-1/Ldb1 is assured in the presence of XRnf12 in the organizer. In the ventrolateral mesoderm, Ldb1 may escape degradation by XRnf12 through interaction with Ldb1-interacting proteins, one of which may be XLMO4 (J. L. Gomez-Skarmeta, personal communication). The putative Ldb1/LMO complex may contribute to complete suppression of Xlim-1/Ldb1 activity in the ventrolateral region, and may participate in a distinct transcriptional regulatory complex. Xlim-1 unbound to Ldb1 may be subject to proteasome-dependent degradation by an unidentified ubiquitin ligase, similar to the case of Drosophila Apterous (Weihe et al., 2001). Image published in: Hiratani I et al. (2003) Copyright © 2003. Image reproduced with permission of the publisher and the copyright holder. This is an Open Access article distributed under the terms of the Creative Commons Attribution License. Larger Image Printer Friendly View

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