Mitosis‐specific histone H3 phosphorylation in vitro in nucleosome structures

Abstract

A mechanism of mitosis‐specific enhancement of histone H3 phosphorylation was analyzed in vitro in terms of nucleosome structure. The incorporation of [32P]phosphate into DNA‐bound H3 was approximately 5–7 times higher than in DNA‐free H3 using the catalytic subunit of cAMP‐dependent protein kinase. The two major N‐terminal serine sites, including the mitosis‐specific site (Ser10) and Ser28, were extensively phosphorylated in the DNA‐bound forms. These phosphorylation patterns were identical to those of nucleosomal H3. In contrast, the H3 in DNA‐free octamers was very slightly phosphorylated. The major site of H3 phosphorylation in DNA‐free H3 was Thr118 in the C‐terminus. Results indicate that DNA‐binding is essential for the high level of mitosis‐specific H3 phosphorylation, and that the nucleosome structure promotes H3 N‐terminal phosphorylation in vitro It also suggests the possibility that H1 prevents H3 phosphorylation during interphase of the cell cycle. Copyright © 1990, Wiley Blackwell. All rights reserved