Article

Ubiquitin Ligase RNF146 Regulates Tankyrase and Axin to Promote Wnt Signaling

University of Birmingham, United Kingdom
PLoS ONE (Impact Factor: 3.53). 07/2011; 6(7):e22595. DOI: 10.1371/journal.pone.0022595
Source: PubMed

ABSTRACT Canonical Wnt signaling is controlled intracellularly by the level of β-catenin protein, which is dependent on Axin scaffolding of a complex that phosphorylates β-catenin to target it for ubiquitylation and proteasomal degradation. This function of Axin is counteracted through relocalization of Axin protein to the Wnt receptor complex to allow for ligand-activated Wnt signaling. AXIN1 and AXIN2 protein levels are regulated by tankyrase-mediated poly(ADP-ribosyl)ation (PARsylation), which destabilizes Axin and promotes signaling. Mechanistically, how tankyrase limits Axin protein accumulation, and how tankyrase levels and activity are regulated for this function, are currently under investigation. By RNAi screening, we identified the RNF146 RING-type ubiquitin E3 ligase as a positive regulator of Wnt signaling that operates with tankyrase to maintain low steady-state levels of Axin proteins. RNF146 also destabilizes tankyrases TNKS1 and TNKS2 proteins and, in a reciprocal relationship, tankyrase activity reduces RNF146 protein levels. We show that RNF146, tankyrase, and Axin form a protein complex, and that RNF146 mediates ubiquitylation of all three proteins to target them for proteasomal degradation. RNF146 is a cytoplasmic protein that also prevents tankyrase protein aggregation at a centrosomal location. Tankyrase auto-PARsylation and PARsylation of Axin is known to lead to proteasome-mediated degradation of these proteins, and we demonstrate that, through ubiquitylation, RNF146 mediates this process to regulate Wnt signaling.

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    • "Given that structural and biochemical analyses revealed that the binding specificity of these domains are dependent on the neighboring amino acids surrounding the modified sites [62] [68], these macrodomains will likely enrich for a restricted set of native ADP-ribosylated partners within cells. Besides macrodomains, the WWE domain from RNF146 has also been shown to be responsible for binding PARylated PARP1 and PARP5a [69] [70] [71]. Given that the WWE domain specifically recognizes the smallest structural subunit for PAR, iso-ADP-ribose [72] (c.f. "
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    Proteomics 09/2014; 15(2-3). DOI:10.1002/pmic.201400217 · 3.97 Impact Factor
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    • "Previously , Stegmeier lab revealed that Axin stability is regulated by Tankyrase and Tankyrase-mediated poly-ADP-ribose modification (PARsylation) of Axin is linked to Axin polyubiquitylation and subsequent degradation by the proteasome (Huang et al., 2009). Later, RNF146 was uncovered to be the E3 ligase for mediating Tankyrase-dependent degradation of Axin, thus playing a positive role in Wnt signaling (Callow et al., 2011; Zhang et al., 2011). Ubiquitin-specific protease 34 (USP34) is also reported to associate with Axin and control its levels, whereby modulating Wnt signaling (Lui et al., 2011). "
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    • "4. Ubiquitin ligase RNF146 (RING finger protein 146) RNF146 is a RING-domain E3 ubiquitin ligase. RNF146 can act as a positive regulator of Wnt signaling through ubiquitylating and destabilizing Axin and tankyrase (Callow et al, 2011). 5. C/EBPβ, Shikonin and Testosterone CCAAT/enhancer binding protein β (C/EBPβ) is rapidly induced in early stages of adipogenesis and is responsible for transcriptional induction of Peroxisome proliferatoractivated receptor γ (PPARγ) and C/EBPα by maintaining active Wnt/β-catenin signaling, after addition of adipogenic inducers. "
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