Showing papers on "Bromodomain published in 1987"

Postsynthetic acetylation of histones during the cell cycle: a general function for the displacement of histones during chromatin rearrangements

Abstract: Postsynthetic acetylation of core histones exhibits a peak during S-phase of the Physarum cell cycle. The maximum 3H-acetate incorporation precedes the maximum of histone synthesis. Acetate is incorporated into all core histones during S-phase, but only into H2A and H2B during G2-period. Resolution of acetylated H4-subspecies reveals acetate incorporation into preexisting H4, but not into newly synthesized molecules during mitosis and early S-phase. In a protamine competition assay histones from S-phase chromatin are released at lower protamine concentrations as compared to the lower acetylated G2-chromatin. We demonstrate a preferential release of highly acetylated H4-subspecies at low protamine concentrations. Our results fit into a general model of the relationship between histone acetylation and chromatin assembly. According to this model acetylation of core histones would serve as a signal for displacement of histones from nucleosomes by modulating histone-protein or histone-DNA interactions. We propose that this mechanism operates during DNA-replication and transcription, as well as during other chromatin rearrangements.

Structural studies of acetylated and control inner core histones

Abstract: The role of acetylation on the conformation and association state of the inner core histone octamer isolated from HeLa cells was examined. Preparation of suitable quantities of pure acetylated and control inner core histones from HeLa cells required the development of a new preparative procedure. The results from size-exclusion high-performance liquid chromatography and sedimentation equilibrium studies indicated that acetylated inner core histones associate to species larger than the octamer and form a more stable complex. Circular dichroism studies demonstrated that the amount of alpha-helix increases with increasing association of the histones. Furthermore, acetylation results in an increase in the amount of alpha-helix, perhaps coupled through its effect on the association state. At high protein concentration and elevated temperature, the acetylated sample displays a greater increase in beta-sheet content, relative to the control sample. This increase in beta-sheet content may be induced during the association of the acetylated sample to species larger than the octamer. There is a marked effect on the conformation of both acetylated and control inner core histones as a function of protein concentration, ionic strength, and temperature. The difference in conformational flexibility and association state of the acetylated vs. the control inner histone core may play a significant role in the control of transcription in the nucleus.