Phosphorylation of H1 histones in normal and transformed mouse cells

The phosphorylation of the NH2- and COOH-terminal regions of H1 histones from normal mouse mammary glands, a mouse breast tumor (D1 tumor) and LM/TK- cells was compared. Chromatographic resolution of H1 subtypes revealed that the normal and transformed cells expressed the same H1 subtypes. Bisection of purified 32P-labeled H1 histones with N-bromosuccinimide, followed by fractionation of the NH2- and COOH-terminal regions of the molecules on Biogel P-60, demonstrated that explants of normal mouse breast tissue preferentially phosphorylated the NH2-terminal region (61% of the 32P) while the D1 tumor preferentially phosphorylated the COOH-terminal region (60% of the 32P). In keeping with numerous other examples, LM/TK- cells in culture also preferentially phosphorylated the COOH-terminal region of the H1 molecule (64% of the 32P).