title: Identification and characterization of nuclear and nucleolar localization signals in 58-kDa microspherule protein (MSP58).
abstract: BACKGROUND
  MSP58 is a nucleolar protein associated with rRNA transcription and cell proliferation. Its mechanism of translocation into the nucleus or the nucleolus, however, is not entirely known. In order to address this lack, the present study aims to determine a crucial part of this mechanism: the nuclear localization signal (NLS) and the nucleolar localization signal (NoLS) associated with the MSP58 protein.
  
  
  RESULTS
  We have identified and characterized two NLSs in MSP58. The first is located between residues 32 and 56 (NLS1) and constitutes three clusters of basic amino acids (KRASSQALGTIPKRRSSSRFIKRKK); the second is situated between residues 113 and 123 (NLS2) and harbors a monopartite signal (PGLTKRVKKSK). Both NLS1 and NLS2 are highly conserved among different vertebrate species. Notably, one bipartite motif within the NLS1 (residues 44-56) appears to be absolutely necessary for MSP58 nucleolar localization. By yeast two-hybrid, pull-down, and coimmunoprecipitation analysis, we show that MSP58 binds to importin α1 and α6, suggesting that nuclear targeting of MSP58 utilizes a receptor-mediated and energy-dependent import mechanism. Functionally, our data show that both nuclear and nucleolar localization of MSP58 are crucial for transcriptional regulation on p21 and ribosomal RNA genes, and context-dependent effects on cell proliferation.
  
  
  CONCLUSIONS
  Results suggest that MSP58 subnuclear localization is regulated by two nuclear import signals, and that proper subcellular localization of MSP58 is critical for its role in transcriptional regulation. Our study reveals a molecular mechanism that controls nuclear and nucleolar localization of MSP58, a finding that might help future researchers understand the MSP58 biological signaling pathway.
authors.affiliation: Institute of Bioinformatics and Biosignal Transduction, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan, 70101, Taiwan, ROC. ben891121@hotmail.com.
authors.forename: Chuan-Pin
authors.initials: CP
authors.lastname: Yang
authors.affiliation: Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, 70101, Taiwan, ROC. chiangcw@mail.ncku.edu.tw.|Infectious Diseases and Signaling Research Center, National Cheng Kung University, Tainan, 70101, Taiwan, ROC. chiangcw@mail.ncku.edu.tw.
authors.forename: Chi-Wu
authors.initials: CW
authors.lastname: Chiang
authors.affiliation: Center for Translational Research in Biomedical Sciences, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, 83301, Taiwan, ROC. chench7@gmail.com.|Department of Applied Chemistry, National Chi Nan University, Puli, Nantou, 54561, Taiwan, ROC. chench7@gmail.com.
authors.forename: Chang-Han
authors.initials: CH
authors.lastname: Chen
authors.affiliation: Center for Neurotrauma and Neuroregeneration, Taipei Medical University, Taipei, 11031, Taiwan, ROC. yclee@tmu.edu.tw.|Program for Neural Regenerative Medicine, College of Medical Science and Technology, Taipei Medical University, Taipei, 11031, Taiwan, ROC. yclee@tmu.edu.tw.
authors.forename: Yi-Chao
authors.initials: YC
authors.lastname: Lee
authors.affiliation: Institute of Bioinformatics and Biosignal Transduction, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan, 70101, Taiwan, ROC. khlin@amazingic.com.
authors.forename: Mei-Hsiang
authors.initials: MH
authors.lastname: Wu
authors.affiliation: Department of Pharmacology, College of Medicine, National Cheng Kung University, Tainan, 70101, Taiwan, ROC. u9403067@cmu.edu.tw.
authors.forename: Yi-Huan
authors.initials: YH
authors.lastname: Tsou
authors.affiliation: Institute of Molecular Medicine, College of Medicine, National Cheng Kung University, Tainan, 70101, Taiwan, ROC. yusanyang@gmail.com.
authors.forename: Yu-San
authors.initials: YS
authors.lastname: Yang
authors.affiliation: Department of Pharmacology, College of Medicine, National Cheng Kung University, Tainan, 70101, Taiwan, ROC. wcchang@mail.ncku.edu.tw.|Infectious Diseases and Signaling Research Center, National Cheng Kung University, Tainan, 70101, Taiwan, ROC. wcchang@mail.ncku.edu.tw.|Graduate Institute of Medical Sciences, College of Medicine, Taipei Medical University, Taipei, 11031, Taiwan, ROC. wcchang@mail.ncku.edu.tw.|Center for Neurotrauma and Neuroregeneration, Taipei Medical University, Taipei, 11031, Taiwan, ROC. wcchang@mail.ncku.edu.tw.
authors.forename: Wen-Chang
authors.initials: WC
authors.lastname: Chang
authors.affiliation: Institute of Bioinformatics and Biosignal Transduction, College of Bioscience and Biotechnology, National Cheng Kung University, Tainan, 70101, Taiwan, ROC. lindy@mail.ncku.edu.tw.|Department of Pharmacology, College of Medicine, National Cheng Kung University, Tainan, 70101, Taiwan, ROC. lindy@mail.ncku.edu.tw.|Infectious Diseases and Signaling Research Center, National Cheng Kung University, Tainan, 70101, Taiwan, ROC. lindy@mail.ncku.edu.tw.|Institute for Cancer Biology and Drug Discovery, College of Medical Science and Technology, Taipei Medical University, Taipei, 11031, Taiwan, ROC. lindy@mail.ncku.edu.tw.
authors.forename: Ding-Yen
authors.initials: DY
authors.lastname: Lin
mesh_terms: D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D002466:Cell Nucleolus / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism*; D006801:Humans; D019913:Nuclear Localization Signals / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D016415:Sequence Alignment
chemical_list: C113292:MCRS1 protein, human; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D016601:RNA-Binding Proteins