Cytoplasmic pool of histone H1 in mammalian cells

Two types of cell populations, nondividing mouse liver cells and exponentially growing Friend erythroleukemia cells, were studied for the presence of a histone H1 pool in the cytoplasm. Purified cytoplasmic fractions were extracted with 5% perchloric acid and the resulting protein preparation was characterized by two types of electrophoresis, gel filtration, peptide mapping, ELISA and immunoblotting. The occurrence of significant quantities of H1 in isolated cytoplasmic fractions was confirmed by indirect immunofluorescence on whole cells. The existence of a cytoplasmic pool of H1 contrasts with the lack of detectable amounts of core histones in the cytoplasm. This indicates that the observed H1 pool is not just a reflection of its cytoplasmic synthesis but probably has some functional significance.