Nucleoplasmin Binds Histone H2A-H2B Dimers through Its Distal Face

• Published in: The Journal of biological chemistry 2010-10, Vol.285 (44), p.33771-33778
• Main Authors: Ramos, Isbaal, Martín-Benito, Jaime, Finn, Ron, Bretaña, Laura, Aloria, Kerman, Arizmendi, Jesús M., Ausió, Juan, Muga, Arturo, Valpuesta, José M., Prado, Adelina
• Format: Article
• Language: English
• Subjects: Animals; Dimerization; Electron Microscopy (EM); Histones; Histones - chemistry; Mass Spectrometry (MS); Mass Spectrometry - methods; Microscopy, Electron - methods; Molecular Biophysics; Nuclear Chaperone; Nucleoplasmin; Nucleoplasmins - chemistry; Phosphorylation; Protein Folding; Protein Interaction Mapping; Protein Structure; Protein Structure and Folding; Protein Structure, Tertiary; Protein-Protein Interactions; Ultracentrifugation; Xenopus laevis - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M110.150664

Nucleoplasmin (NP) is a pentameric chaperone that regulates the condensation state of chromatin extracting specific basic proteins from sperm chromatin and depositing H2A-H2B histone dimers. It has been proposed that histones could bind to either the lateral or distal face of the pentameric structure. Here, we combine different biochemical and biophysical techniques to show that natural, hyperphosphorylated NP can bind five H2A-H2B dimers and that the amount of bound ligand depends on the overall charge (phosphorylation level) of the chaperone. Three-dimensional reconstruction of NP/H2A-H2B complex carried out by electron microscopy reveals that histones interact with the chaperone distal face. Limited proteolysis and mass spectrometry indicate that the interaction results in protection of the histone fold and most of the H2A and H2B C-terminal tails. This structural information can help to understand the function of NP as a histone chaperone.