Level Of Deacetylation Research Articles

Regulation of histone acetylation during macronuclear differentiation in Tetrahymena: Evidence for control at the level of acetylation and deacetylation

During the postzygotic period of the sexual cycle (conjugation) in the ciliated protozoan, Tetrahymena, daughter products from a single micronuclear mitotic division develop into new macronuclei (anlagen) or new micronuclei depending upon their cytoplasmic location. In this study we have monitored the status of histone acetylation in synchronous populations of developing nuclei isolated from conjugating cells. Particular attention has been paid to the level of histone acetylation in new macronuclei following their differentiation from micronuclei. Like micronuclei isolated from vegetative cells (Vavra et al., 1982), micronuclei from conjugating cells (5 hr, 10–12 hr, and 15–16 hr) contain little if any acetylated histone and incorporate little postsynthetic acetate under any of our experimental conditions. In contrast, young new macronuclei (4C, 10–12 hr) incorporate significant amounts of acetate in vitro and in vivo provided that sodium butyrate is included during the labeling period. These results suggest that 4C anlagen contain both active acetylase and deacetylase activities even though the actual steady state level of acetylation found in these nuclei is low, more like that of micronuclei. At later stages of macronuclear maturation (8C, 15–16 hr), inner histones are hyperacetylated in a manner similar to parental, fully differentiated macronuclei. Furthermore, 8C anlagen incorporate acetate well even in the absence of sodium butyrate. Taken together these results suggest that endogenous deacetylase enzymes become either down-regulated and/or the rate of histone acetylases increases markedly during macronuclear differentiation.

The Translocation of Sulphonamides in Higher Plants

The acetylation of both amino groups on sulphanilamide has been demon strated by paper chromatography of sap expressed from broad beans treated with sulphanilamide through the roots. Deacetylation of N1and N4-acetylsulphanila mides occurred in the leaves of treated plants and the N4-acetyl compound was also acetylated to yield the N1 : N4-diacetylsulphanilamide. About 30 per cent, of the sulphanilamide entering broad-bean roots was acetylated in the roots, the maximum proportion of the N4-acetyl compound being reached after 7 days. Deacetylation is a more limited process but reaches a steady state after the same time. Low levels of acetylation and deacetylation were recorded in wheat. The amounts of sulphanilamide and N4-acetylsulphanilamide entering and accumulating in the various tissues were calculated on a water-uptake basis and these data show that the main site of acetylation is in the roots and that deacetyla tion occurs to a limited extent in the roots but predominates in stems and leaves.