Effects of butyric acid on cell cycle regulation and induction of histone H1 ∘ in mouse cells and tissue culture: Inducibility of H1 ∘ in the late S-G2 phase of the cell cycle

Abstract We have examined the regulation of the synthesis of histone H1 ∘ in cultured mammalian cells treated with butyric acid. Treatment of cells with the inducer results in the arrest of synthesis of DNA and the other histones, while increasing the synthesis of H1 ∘ by a factor of 11. The induction of H1 ∘ by butyric acid occurs in a pulse with a peak at six hours, followed by a decrease to negligible levels. This pulse-like induction appears to be due to the fact that the cells are inducible for H1 ∘ only in the late S or G2 phases of the cell cycle. This, coupled with the fact that butyric acid blocks cells in G1, results in the burst of H1 ∘ synthesis after addition of the inducer. The G1 block provoked by butyric acid does not appear to result from the accumulation of H1 ∘. Removal of butyric acid from G1-blocked cells resulted in the resumption of cellular proliferation without prior loss of H1 ∘, demonstrating that the presence of this histone is not sufficient to prevent cellular proliferation.