title: NBP-45, a novel nucleosomal binding protein with a tissue-specific and developmentally regulated expression.
abstract: Here we characterize a novel murine nuclear protein, which we named NBP-45, that is related to the ubiquitous nuclear proteins HMG-14/-17, binds specifically to nucleosome core particles, and can function as a transcriptional activator. NBP-45 mRNA is expressed at low levels and in variable amounts in all mouse tissues tested but is especially abundant in RNA extracted from 7-day-old mouse embryos, suggesting that it functions in early embryonic development. NBP-45 is composed of 406 amino acids and is encoded by a single size transcript. The region spanning the N-terminal 85 amino acids contains three segments that are highly homologous to functionally important domains in the HMG-14/-17 protein family: the nuclear localization signal, the nucleosome binding domain, and the chromatin unfolding domain. The protein region spanning the C-terminal 321 amino acids has a 42% content of negatively charged residues. The first 23 amino acids contain a region necessary for nuclear entry of the protein, the region spanning residues 12-40 is the main nucleosomal binding domain of the protein, and the negatively charged, C-terminal domain is necessary for transcription activation. The functional domains of NBP-45 are indicative of a nuclear protein that binds to nucleosomes, thereby creating a chromatin region of high local negative charge. Our studies establish the nucleosomal binding domain as a protein motif that is present in other than just the ubiquitous HMG-14/-17 proteins. We suggest that the nucleosomal binding domain motif is a protein module that facilitates binding to nucleosomes in chromatin.
authors.affiliation: Institute of Computational Biology Branch, National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: H
authors.initials: H
authors.lastname: Shirakawa
authors.forename: D
authors.initials: D
authors.lastname: Landsman
authors.forename: Y V
authors.initials: YV
authors.lastname: Postnikov
authors.forename: M
authors.initials: M
authors.lastname: Bustin
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics*; D002843:Chromatin / Q000378:metabolism; D003001:Cloning, Molecular; D005455:Fluorescent Antibody Technique; D018507:Gene Expression Regulation, Developmental / Q000235:genetics*; D024001:HMGN Proteins; D006367:HeLa Cells; D006609:High Mobility Group Proteins / Q000737:chemistry / Q000235:genetics; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics*; D009707:Nucleosomes / Q000378:metabolism*; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism; D016415:Sequence Alignment; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics*; D014162:Transfection
chemical_list: D002352:Carrier Proteins; D002843:Chromatin; D024001:HMGN Proteins; D006609:High Mobility Group Proteins; C498963:Hmgn5 protein, mouse; D009687:Nuclear Proteins; D009707:Nucleosomes; D012333:RNA, Messenger; D015534:Trans-Activators