Expression and purification of the full murine NPM2 and study of its interaction with protamines and histones

• Characterization of the entire mouse M.NPM2 protein.
• Determination of sites of interaction of M.NPM2 with histones and mouse protamines.
• Use of crosslinking mass spectrometry to determine protein-protein interactions.
• Analysis of the C-terminal NPM2 unfolding.

Mouse nucleoplasmin M.NPM2 was recombinantly expressed and the protein consisting of the complete sequence was purified and characterized. Similar to its Xenopus laevis X.NPM2 counterpart, the protein forms stable pentameric complexes and exhibits an almost undistinguishable hydrodynamic ionic strength-dependent unfolding behavior. The interaction of N.PM2 with histones and mouse P1/P2 protamines revealed that these chromosomal proteins bind preferentially to the distal part of the nucleoplasmin pentamer. Moreover, the present work highlights the critical role played by histones H2B and H4 in the association of the histone H2A-H2B dimers and histone octamer with nucleoplasmin.