Figure 7.

Assembly of somatic H1 on erythrocyte chromatin inhibits replication in extracts containing NPL. (A) Permeable erythrocyte nuclei were incubated (140 ng of DNA/μl of extract) in extract without (CON) or with histone H1c (H1; 5.68 μM) for 15 or 60 min as indicated. The chromatin-associated proteins from unincubated nuclei (XEN) and from incubated nuclei were isolated and analyzed as described in Figure 4. The positions of the embryonic linker histone B4, somatic linker histones H1 and H1⁰, somatic mouse linker histone H1c, and core histones, H3, H2B, H2A, and H4 are indicated. Protein levels were quantitated by densitometry and normalized to the core histones in each sample. (B) Permeable erythrocyte nuclei were incubated for 8 h in extract without (0 μM H1) or with increasing concentrations of H1c (3.41, 4.54, and 5.68 μM H1). The samples were processed as described in MATERIALS AND METHODS. DNA replication is expressed as a percentage of the control sample that was designated as 100%.