Cell cycle-dependent suppressive effect of histone H1 on mitosis-specific H3 phosphorylation

To analyze the mechanism by which histone H3 phosphorylation occurs specifically during mitosis, the effect of H1 on mitosis-specific H3 phosphorylation (Ser-10) was investigated in nucleosomes. H1 interaction with H1-depleted nucleosomes suppressed H3 phosphorylation including Ser-10 by approximately 50%. However, H1 interaction with DNA-free histone octamers failed to suppress H3 phosphorylation. The extent of suppression of H3 phosphorylation in nucleosomes with H1 prepared from synchronized HeLa cells was cell cycle-dependent. Binding with a highly phosphorylated mitotic H1 produced the least suppression of H3 phosphorylation, whereas binding with a lower H1 phosphorylation from G1 phase resulted in the greatest suppression. The results suggest that 1) mitotic H3 phosphorylation is suppressed with a lower level of H1 phosphorylation during interphase and 2) highly phosphorylated H1 during mitosis partially releases the suppression of mitotic H3 phosphorylation.