title: Ribosomal stress induces processing of Mybbp1a and its translocation from the nucleolus to the nucleoplasm.
abstract: Myb-binding protein 1a (Mybbp1a) was originally identified as a c-myb proto-oncogene product (c-Myb)-interacting protein, and also binds to various other transcription factors. The 160-kDa Mybbp1a protein (p160(MBP)) is ubiquitously expressed and is post-translationally processed in some types of cells to generate an amino-terminal 67 kDa fragment (p67(MBP)). Despite its interaction with various transcription factors, Mybbp1a is localized predominantly, but not exclusively, in nucleoli. Here, we have purified the two Mybbp1a-containing complexes. The smaller complex contained p67(MBP) and p140(MBP), which lacked the C-terminal region of p160(MBP) containing the nucleolar localization sequences. The larger complex contained the intact p160(MBP) and various ribosomal subunits. Treatment of cells with actinomycin D (ActD), cisplatin or UV, all of which inhibit ribosome biogenesis, induced processing of p160(MBP) into p140(MBP) and p67(MBP). ActD, cisplatin and UV also induced a translocation of Mybbp1a from the nucleolus to the nucleoplasm. Both small and large Mybbp1a complexes contained nucleophosmin and nucleolin. In contrast, nucleostemin was detected only in the large complex, while the cell cycle-regulated protein EBP1 was only in the small complex. These results suggest that Mybbp1a may connect the ribosome biogenesis and the Myb-dependent transcription, which controls cell cycle progression and proliferation.
authors.affiliation: Laboratory of Molecular Genetics, RIKEN Tsukuba Institute, 3-1-1 Koyadai, Tsukuba, Ibaraki 305-0074, Japan.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Yamauchi
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Keough
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Gonda
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Ishii
mesh_terms: D021581:Active Transport, Cell Nucleus; D048868:Adaptor Proteins, Signal Transducing / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D002466:Cell Nucleolus / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D002945:Cisplatin / Q000494:pharmacology; D004268:DNA-Binding Proteins; D003609:Dactinomycin / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D041681:NIH 3T3 Cells; D019913:Nuclear Localization Signals / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins / Q000378:metabolism*; D000090243:Nucleophosmin; D010750:Phosphoproteins / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D000090063:Proto-Oncogene Mas; D016601:RNA-Binding Proteins / Q000378:metabolism / Q000502:physiology; D012270:Ribosomes / Q000502:physiology*; D014157:Transcription Factors; D000097796:Nucleolin
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002945:Cisplatin; D004268:DNA-Binding Proteins; D003609:Dactinomycin; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; D000090243:Nucleophosmin; D010750:Phosphoproteins; D011500:Protein Synthesis Inhibitors; D000090063:Proto-Oncogene Mas; D016601:RNA-Binding Proteins; D014157:Transcription Factors; D000097796:Nucleolin; C000715470:MAS1 protein, human; C491719:MYBBP1A protein, human; C000716967:NPM1 protein, human; C101633:PA2G4 protein, human