DEVELOPMENTALLY-REGULATED CHROMATIN ACETYLATION AND HISTONE H1(0) ACCUMULATION

There exists a close relationship between core histone acetylation and the induced expression of the histone H1(0) gene. We took advantage o f this fact to evaluate the influence of chromatin hyperacetylation on the developmentally regulated expression of this specific gene. In th is study, the in situ immunodetection approach has been used to analyz e both the acetylated histone H4 isoforms and histone H1(0) accumulati on during early Xenopus laevis development. We have chosen two stages of development, gastrula stage, when H1(0) is not expressed and is not inducible by butyrate treatment, and stage 27 when H1(0) is not expre ssed but is inducible by butyrate. At stage 27 of development, the ear ly induced accumulation of histone H1(0) under butyrate treatment, occ urs mainly in tissues that express the protein normally during later d evelopment. These experiments suggest that histone acetylation may be part of a pathway which, in a specific set of cells, keeps H1(0) and p robably a series of specific genes, competent for transcription, but c ell-specific factors are involved in the induced expression of these g enes.