Native PAGE of a titration of histone octamers (A) and mouse protamines P1/P2 (B) with increasing amounts of M.NPM2. ). In this type of analysis, NPM2: histone/protamine complexes display a complex ‘shift’ and are unable to enter the gel. (C) Amino acid sequence of mouse NPM2 and core histones H2A, H2B and H4, with interaction sites determined through CXMS data (Supp. Table 1a) highlighted in red. Three peptide sequences in NPM2 represent strong cross-linking candidates with sequences in H2A, H2B and H4 (highlighted in red). Gallus gallus H2A NCBI Reference Sequence: AAC60008.1, G. gallus H2B NCBI Reference Sequence: AAC60000.1, G. gallus H4 NCBI Reference Sequence: NP_001032932.1. (D) Amino acid sequence of mouse NPM2, P1 and P2, with possible interaction sites determined through CXMS data (Supp. Table 1a) highlighted in red. Three peptide sequences within M.NPM2 represent possible cross-linking candidates. M. musculus NPM2 NCBI Reference Sequence: NP_851990.2; M. musculus P1 NCBI Reference Sequence: NP_038665.1; M. musculus P2 NCBI Reference Sequence: P07978.1.