3utm | pdb_00003utm
Crystal structure of a mouse Tankyrase-Axin complex
Structural highlights
Function[TNKS1_MOUSE] Poly-ADP-ribosyltransferase involved in various processes such as Wnt signaling pathway, telomere length and vesicle trafficking. Acts as an activator of the Wnt signaling pathway by mediating poly-ADP-ribosylation (PARsylation) of AXIN1 and AXIN2, 2 key components of the beta-catenin destruction complex: poly-ADP-ribosylated target proteins are recognized by RNF146, which mediates their ubiquitination and subsequent degradation. Also mediates PARsylation of BLZF1 and CASC3, followed by recruitment of RNF146 and subsequent ubiquitination. Mediates PARsylation of TERF1, thereby contributing to the regulation of telomere length. Involved in centrosome maturation during prometaphase by mediating PARsylation of HEPACAM2/MIKI. May also regulate vesicle trafficking and modulate the subcellular distribution of SLC2A4/GLUT4-vesicles. May be involved in spindle pole assembly through PARsylation of NUMA1 (By similarity). [AXIN1_MOUSE] Component of the beta-catenin destruction complex required for regulating CTNNB1 levels through phosphorylation and ubiquitination, and modulating Wnt-signaling (By similarity). Controls dorsoventral patterning via two opposing effects; down-regulates CTNNB1 to inhibit the Wnt signaling pathway and ventralize embryos, but also dorsalizes embryos by activating a Wnt-independent JNK signaling pathway. In Wnt signaling, probably facilitates the phosphorylation of CTNNB1 and APC by GSK3B. Likely to function as a tumor suppressor. Facilitates the phosphorylation of TP53 by HIPK2 upon ultraviolet irradiation. Enhances TGF-beta signaling by recruiting the RNF111 E3 ubiquitin ligase and promoting the degradation of inhibitory SMAD7 (By similarity). Also component of the AXIN1-HIPK2-TP53 complex which controls cell growth, apoptosis and development.[1] [2] [3] Publication Abstract from PubMedAxin is a tumor suppressor and a key negative regulator of the Wnt/beta-catenin signaling pathway. Axin turnover is controlled by its poly-ADP-ribosylation catalyzed by tankyrase (TNKS), which requires the direct interaction of Axin with TNKS. This interaction is thus an attractive drug target for treating cancers, brain injuries, and other diseases where beta-catenin is involved. Here we report the crystal structure of a mouse TNKS1 fragment containing ankyrin-repeat clusters 2 and 3 (ARC2-3) in a complex with the TNKS-binding domain of mouse Axin1. Surprisingly, we found that Axin contains two discrete TNKS-binding segments, both of which bind simultaneously to the two ARC2 domains in the ARC2-3 homodimer. Our crystal structure shows that in each TNKS-binding segment of Axin there is a conserved glycine residue that lies in the bottom of a narrow "gate" formed by two parallel tyrosine side chains on the TNKS surface. This glycine-selection gate is crucial for TNKS-Axin interactions, as mutation of the TNKS gate-forming residues, or mutation of either glycine residue in the two Axin segments, completely abolishes the binding of the corresponding Axin segment to TNKS. The bivalent binding of Axin to TNKS is required for Axin turnover, since mutations in either gate-binding glycine residue in Axin lead to Axin stabilization in the cell. In addition, our analyses also reveal the structural basis for TNKS substrate recruitment, and shed light on the overall structure of TNKS that should help in developing specific inhibitors of Wnt/beta-catenin signaling. Crystal structure of a Tankyrase-Axin complex and its implications for Axin turnover and Tankyrase substrate recruitment.,Morrone S, Cheng Z, Moon RT, Cong F, Xu W Proc Natl Acad Sci U S A. 2012 Jan 31;109(5):1500-5. Epub 2012 Jan 17. PMID:22307604[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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