title: The BTB protein MEL-26 is a substrate-specific adaptor of the CUL-3 ubiquitin-ligase.
abstract: Many biological processes, such as development and cell cycle progression are tightly controlled by selective ubiquitin-dependent degradation of key substrates. In this pathway, the E3-ligase recognizes the substrate and targets it for degradation by the 26S proteasome. The SCF (Skp1-Cul1-F-box) and ECS (Elongin C-Cul2-SOCS box) complexes are two well-defined cullin-based E3-ligases. The cullin subunits serve a scaffolding function and interact through their C terminus with the RING-finger-containing protein Hrt1/Roc1/Rbx1, and through their N terminus with Skp1 or Elongin C, respectively. In Caenorhabditis elegans, the ubiquitin-ligase activity of the CUL-3 complex is required for degradation of the microtubule-severing protein MEI-1/katanin at the meiosis-to-mitosis transition. However, the molecular composition of this cullin-based E3-ligase is not known. Here we identified the BTB-containing protein MEL-26 as a component required for degradation of MEI-1 in vivo. Importantly, MEL-26 specifically interacts with CUL-3 and MEI-1 in vivo and in vitro, and displays properties of a substrate-specific adaptor. Our results suggest that BTB-containing proteins may generally function as substrate-specific adaptors in Cul3-based E3-ubiquitin ligases.
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000483:Alleles; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D044842:Cullin Proteins; D008025:Ligases / Q000737:chemistry* / Q000378:metabolism*; D046911:Macromolecular Substances; D008540:Meiosis; D008870:Microtubules / Q000378:metabolism; D008938:Mitosis; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D021122:Protein Subunits / Q000378:metabolism; D034622:RNA Interference; D013379:Substrate Specificity; D044767:Ubiquitin-Protein Ligases
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D044842:Cullin Proteins; D046911:Macromolecular Substances; C114960:Mel-26 protein, C elegans; D021122:Protein Subunits; D044767:Ubiquitin-Protein Ligases; D000251:Adenosine Triphosphatases; C086678:MEI-1 protein, C elegans; D008025:Ligases