Accumulation of Histone H1° during Chemically Induced Differentiation of Murine Neuroblastoma Cells

Abstract

A basic nuclear protein with properties similar to lysine-rich histones accumulates during differentiation in vitro of C1300 murine neuroblastoma cells (clone Neuro-2a) induced by n-butyrate, dimethyl sulfoxide, hexamethylene bisacetamide or 1,6-dibutyryl-AMP. A protein with the same electrophoretic properties, present in adult mouse brain cell nuclei in amounts similar to those in the induced neuroblastoma cells, was characterized as histone H1.degree.. Digestion of the 2 proteins with Staphylococcus aureus V8 protease gives identical peptide maps (sharing no common peptides with those of histones H1A or H1B), which indicates that the induced protein qualifies as H1.degree.. Accumulation of histone H1.degree. in neuroblastoma cell nuclei accompanies shutoff of DNA synthesis and transgression of the cells into a G1-phase resting state. Upon removal of n-butyrate the cells resume proliferation and their H1.degree. content decreases, indicating an association of H1.degree. with the resting state during which differentiated cellular functions are expressed.