Species- and cell-specific expression of H1 histones in tissue culture cells

The H1 histones of 25 tissue culture cell types of rat, mouse, human, and Chinese hamster origin were studied by ion-exchange chromatography. Fractionation of H1 histones revealed that each cell type expressed multiple H1 histone subfractions. The average number of four subfractions was the same as seen in tissues. The individual H1 histones exhibited species-specific chromatographic properties, and different cell lines from a given animal were capable of expressing cell-specific quantities of the H1 histone subtypes. Neither the species- nor cell-specific properties of the H1 histones could be abolished by alkaline phosphatase treatment, but such treatment did reduce the complexity of H1 histone subfractions in SV40-transformed cells. The direct comparison of rat liver and rat hepatoma cell (H-35) H1 histones by chromatographic and electrophoretic methods demonstrated that a cell line was capable of expressing the same variety of H1 histones as the tissue of origin. Variations in the content of H1 histone subtypes were seen in intraspecies comparisons in all four species. The variations were not reduced by recloning selected cells. The variations among subfractions were dramatic for Chinese hamster cell lines CHO, V79, and DON. Smaller variations could be seen in mouse cell lines and numerous genetic mutant human fibroblast cells and HeLa cells, but the latter did not appear to be specifically related to disease state. Since H1 histones link nucleosomes, the packing of nucleosomes in the chromatin of tissue culture cells has the same potential variability as in tissues.