MULTIPLE FUNCTIONS OF DYNAMIC HISTONE ACETYLATION

Besides its role in organizing nuclear DNA, the nuclear matrix is invo lved in specific nuclear functions, including replication, transcripti on, and RNA splicing. It is becoming increasingly evident that nuclear processes are localized to distinct regions in the nucleus. For examp le, transcriptionally active genes and RNA transcripts are found in di screte transcription foci. Current evidence suggests that nuclear matr ix-bound transcriptionally active DNA sequences are in nucleosomes wit h dynamically acetylated histones. Histone acetylation, which precedes transcription, alters nucleosome and chromatin structure, decondensin g the chromatin fibre and making the nucleosomal DNA accessible to tra nscription factors. Histone acetyltransferase and histone deacetylase, which catalyze this rapid acetylation and deacetylation, are associat ed with the internal nuclear matrix. We hypothesize that these enzymes play a role in maintaining the association of the active chromatin do mains with the internal nuclear matrix at sites of ongoing transcripti on. (C) 1994 Wiley-Liss, Inc.