Alteration of Cell Cycle-dependent Histone Phosphorylations by Okadaic Acid

doi:10.1074/jbc.271.22.13197

Alteration of Cell Cycle-dependent Histone Phosphorylations by Okadaic Acid

INDUCTION OF MITOSIS-SPECIFIC H3 PHOSPHORYLATION AND CHROMATIN CONDENSATION IN MAMMALIAN INTERPHASE CELLS*

From the ^‡ Aichi Cancer Center, Research Institute, Laboratory of Cell Biology and
^∥ Laboratory of Ultrastructure Research, Chikusa-ku and the
^¶ Nagoya University, Faculty of Science, Institute of Molecular Biology, Nagoya 464, Japan

^§ To whom corresponding should be addressed:
Aichi Cancer Center, Research Institute, Laboratory of Cell Biology, Chikusa-ku, Nagoya 464, Japan.
Tel.: 052-762-6111 (ext. 8821); Fax: 052-763-5233.

Abstract

Effects of okadaic acid (OA), a protein phosphatase inhibitor, on chromatin structure and phosphorylation of histones were examined using HeLa and N18 cells. The chromatin condensation in HeLa cells was mild and resemble prometaphase nuclei, while the condensation in N18 cells was extensive and chromatin became a compact body. H2A in HeLa cells was extensively and consistently phosphorylated at the same site throughout the cell cycle, and H3 was demonstrated to be phosphorylated at the mitosis-specific site Ser¹⁰. In contrast, H1 phosphorylation was rapidly decreased in most sites within 3 h. The reduction of H1 phosphorylation was accompanied by a quantitative change in the set of H1 phosphopeptides. During the early phase of the OA treatment, H1 phosphorylation was transiently elevated in tandem, whereas H3 phosphorylation reached a maximum somewhat later. The results suggest that mitosis-specific events (cdc2/H1 kinase activation, H1 superphosphorylation, mitosis-specific H3 phosphorylation and chromatin condensation) induced by OA are sequentially associated. The changes appear to reflect a molecular mechanism similar to that operating in normal mitosis.

Footnotes

↵* This work was supported in part by The Sagawa Cancer Research Fund, Japan. The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

H

histone

OA

okadaic acid

6-DMAP

6-dimethylaminopurine

PCC

premature chromosome condensation

pp1/pp2A

protein phosphatase 1 and 2A.
- Received February 21, 1996.