title: Identification of a structural and functional domain in xNAP1 involved in protein-protein interactions.
abstract: xNAP1 (Xenopus nucleosome assembly protein) belongs to the family of nucleosome assembly proteins (NAPs) and shares 92% identity with human and mouse NAP1. NAPs have been reported to have a role in nucleosome assembly, cell cycle regulation, cell proliferation and transcriptional control, although the precise function of NAP1 is still not clear. Here we report the identification of a putative domain of xNAP1 by limited proteolysis. This domain has been mapped in the xNAP1 protein sequence to residues 38-282 and thus lacks the acidic sequences at the N- and C-termini. We have studied this domain and related fragments in vitro and by a functional assay involving over-expression of the protein in Xenopus laevis embryos. Analytical ultracentrifugation shows that removal of the acidic N- and C-terminal regions does not prevent the formation of larger multimers, which are predominantly hexadecamers. Injection of mRNA encoding the full-length xNAP1 or the putative domain and other related constructs into Xenopus embryos gave identical phenotypes. These results are discussed in relation to protein-protein interactions between NAP1 octamers and a possible 'squelching' mechanism.
authors.affiliation: Institute of Biomedical and Biomolecular Sciences, University of Portsmouth, Portsmouth PO1 2DT, UK.
authors.forename: Christine
authors.initials: C
authors.lastname: Friedeberg
authors.forename: Garry
authors.initials: G
authors.lastname: Scarlett
authors.forename: John
authors.initials: J
authors.lastname: McGeehan
authors.forename: Anita
authors.initials: A
authors.lastname: Abu-Daya
authors.forename: Matthew
authors.initials: M
authors.lastname: Guille
authors.forename: Geoff
authors.initials: G
authors.lastname: Kneale
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D019521:Body Patterning; D004625:Embryo, Nonmammalian / Q000033:anatomy & histology / Q000378:metabolism; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry* / Q000378:metabolism; D056490:Nucleosome Assembly Protein 1; D010447:Peptide Hydrolases / Q000378:metabolism; D010449:Peptide Mapping; D010641:Phenotype; D017434:Protein Structure, Tertiary; D014461:Ultracentrifugation; D029867:Xenopus Proteins / Q000737:chemistry* / Q000378:metabolism; D014982:Xenopus laevis / Q000033:anatomy & histology / Q000196:embryology* / Q000378:metabolism
chemical_list: C514591:NAP1L1 protein, Xenopus; D009687:Nuclear Proteins; D056490:Nucleosome Assembly Protein 1; D029867:Xenopus Proteins; D010447:Peptide Hydrolases