Dephosphorylation of histones H1 and H3 during the isolation of metaphase chromosomes.

Histones have been extracted from isolated metaphase chromosomes prepared by the method of Wray and Sutbblefield [Exp. Cell Res 59, 469-478 (1970)] and by a Nonidet P-40 detergent procedure based on the method of Wigler and Axel [Nucleic Acids Res. 3, 1463-1471 (1976)]. Analysis of the densitometer profiles of long polyacrylamide gels shows that the mitotic phosphorylations of histone H1 (H1M) and histone H3 are extensively depleted during chromosome isolation. These data indicate that CHO metaphase chromosomes prepared by standard methodologies do not represent in vivo chromosomes with respect to their histone phosphorylations; therefore, current chemical and structural studies of isolated metaphase chromosomes may require further clarification.