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Modulation in proportions of H1 histone subfractions by differential changes in synthesis and turnover during butyrate treatment of neuroblastoma cells.

Mouse neuroblastoma cells treated with millimolar concentrations of butyrate adjusted their recipe of histone H1 subfractions over the course of several days, eventually attaining an enrichment of about 5-fold in H1(0). This adjustment in the proportions of the H1's, which was essentially complete by 4 days, was brought about by changes in synthesis and turnover that were different for each of the three H1 subfractions. As the cells stopped dividing, the synthesis of all histones slowed substantially, but core histones were affected more than the H1's. Transiently, therefore, there was an overproduction of H1's relative to core histones, but the excess H1 was eventually removed by turnover. The very slow turnover of H1(0) and the rapid turnover of H1c were not substantially affected by butyrate treatment, but the turnover of H1ab was greatly accelerated by butyrate. Acetylation of the core histones was not necessary for maintenance of elevated H1(0) levels in the nondividing cells, although we did not rule out its involvement in the initial accumulation of H1(0).