title: Nuclear cereblon modulates transcriptional activity of Ikaros and regulates its downstream target, enkephalin, in human neuroblastoma cells.
abstract: The gene coding cereblon (CRBN) was originally identified in genetic linkage analysis of mild autosomal recessive nonsyndromic intellectual disability. CRBN has broad localization in both the cytoplasm and nucleus. However, the significance of nuclear CRBN remains unknown. In the present study, we aimed to elucidate the role of CRBN in the nucleus. First, we generated a series of CRBN deletion mutants and determined the regions responsible for the nuclear localization. Only CRBN protein lacking the N-terminal region was localized outside of the nucleus, suggesting that the N-terminal region is important for its nuclear localization. CRBN was also identified as a thalidomide-binding protein and component of the cullin-4-containing E3 ubiquitin ligase complex. Thalidomide has been reported to be involved in the regulation of the transcription factor Ikaros by CRBN-mediated degradation. To investigate the nuclear functions of CRBN, we performed co-immunoprecipitation experiments and evaluated the binding of CRBN to Ikaros. As a result, we found that CRBN was associated with Ikaros protein, and the N-terminal region of CRBN was required for Ikaros binding. In luciferase reporter gene experiments, CRBN modulated transcriptional activity of Ikaros. Furthermore, we found that CRBN modulated Ikaros-mediated transcriptional repression of the proenkephalin gene by binding to its promoter region. These results suggest that CRBN binds to Ikaros via its N-terminal region and regulates transcriptional activities of Ikaros and its downstream target, enkephalin.
authors.affiliation: Faculty of Science and Engineering, Waseda University, TWIns, 2-2 Wakamatsu, Shinjuku, Tokyo, 162-8480, Japan.
authors.forename: Takeyoshi
authors.initials: T
authors.lastname: Wada
authors.affiliation: Faculty of Science and Engineering, Waseda University, TWIns, 2-2 Wakamatsu, Shinjuku, Tokyo, 162-8480, Japan; Research Organization for Nano & Life Innovation, Waseda University #03C309, TWIns, 2-2 Wakamatsu, Shinjuku, Tokyo, 162-8480, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Asahi
authors.affiliation: Faculty of Science and Engineering, Waseda University, TWIns, 2-2 Wakamatsu, Shinjuku, Tokyo, 162-8480, Japan; Research Organization for Nano & Life Innovation, Waseda University #03C309, TWIns, 2-2 Wakamatsu, Shinjuku, Tokyo, 162-8480, Japan. Electronic address: naoya.sawamura@gmail.com.
authors.forename: Naoya
authors.initials: N
authors.lastname: Sawamura
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D045744:Cell Line, Tumor; D004745:Enkephalins / Q000378:metabolism*; D006801:Humans; D051740:Ikaros Transcription Factor / Q000235:genetics*; D009447:Neuroblastoma / Q000378:metabolism* / Q000473:pathology; D010447:Peptide Hydrolases / Q000502:physiology*; D011401:Promoter Regions, Genetic; D014158:Transcription, Genetic / Q000502:physiology*; D044767:Ubiquitin-Protein Ligases
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C502543:CRBN protein, human; D004745:Enkephalins; C497239:IKZF1 protein, human; D051740:Ikaros Transcription Factor; D044767:Ubiquitin-Protein Ligases; D010447:Peptide Hydrolases
keywords: Cereblon; Enkephalin; Ikaros; Nuclear localization; Transcriptional regulation