The H1 histones and their interphase phosphorylated states in differentiated and undifferentiated cell lines derived...

The histone H1 fraction from the murine embryonal carcinoma cell line F9 can be resolved by two-dimensional gel electrophoresis into at least 15 components. Ten of these components incorporate 32P from administered orthophosphate. The digestion of 3H- and 32P-labeled samples with alkaline phosphatase indicates that this cell line has at least five H1 subtypes, three of which have not been observed in the mouse before. Every subtype is phosphorylated to some extent. There are, however, striking differences among them in the degree of phosphorylation in interphase, both in the proportion of molecules present as phosphorylated forms and in the numbers of phosphate groups per molecule. Phosphorylations of two types are discernible; most phosphorylations do not significantly affect the mobility of the protein in sodium dodecyl sulfate-containing gels but one does, probably reflecting a phosphorylation-induced alteration in protein conformation. Four subtypes undergo only the first type of phosphorylation; the other subtype undergoes both types of phosphorylation. The same 5 subtypes are also present in two other independently derived embryonal carcinoma cell lines. In contrast, two differentiated (endoderm-like) cell lines derived from teratocarcinomas lack H1b, and one also lacks H1d. Our results are consistent with the view that the H1 subtypes differ from each other functionally. They also show that neither H1b nor H1d is essential for cell division.