Histone phosphorylation in explants of mouse mammary glands and tumors.

Rates of histone phosphorylation were measured in explants of mammary glands from mouse strains with high and low tumor incidence. Explants of hormone dependent and independent mouse mammary tumors were also investigated. All mouse strains studied showed predominant phosphorylation of H2A histone at serine and threonine residues. No differences in rates of H2A phosphorylation in glands were found between strains having different mammary tumor susceptibility. Hormone-dependent GR mouse mammary tumors also showed high H2A phosphorylation, but in some tumors also H1 and H3 were phosphorylated. Hormone-dependent GR tumors had 2-5 times higher histone phosphorylation at serine and threonine than hormone-independent tumors.