SUBCELLULAR LOCATION OF ENZYMES INVOLVED IN-CORE HISTONE ACETYLATION

Multiple enzyme forms of histone deacetylase and histone acetyltransfe rase exist in germinating maize embryos. We analyzed the association o f the different enzymes to chromatin by ion exchange chromatography of subcellular fractions from different time points of embryo germinatio n. The vast majority of histone deacetylase HD-1A was not bound to chr omatin, since it was solubilized during chromatin isolation, regardles s of its phosphorylation state and the phase of embryo germination. In contrast, HD-2 was chromatin bound during the entire germination path way. Histone deacetylase HD-1B was present in a chromatin-bound and a soluble form; the ratio between these two forms changed during germina tion. Both nuclear histone acetyltransferases, HAT-A1 and HAT-A2, were tightly chromatin-bound and could only be released from chromatin by salt extraction. To test whether histone acetyltransferases or deacety lases are associated with the nuclear matrix, we analyzed nuclear matr ix preparations from yeast, Physarum, and maize step by step for both enzyme activities. This analysis confirmed that part of the activity i s chromatin bound, but no significant enzyme activity could be found i n the final nuclear matrix, regardless of the preparation protocol. Th is result was further substantiated by detailed analysis of histone de acetylases and acetyltransferases during cellular fractionation and nu clear matrix preparation of chicken erythrocytes. Altogether our resul ts suggest that the participation of these enzymes in different nuclea r processes may partly be regulated by a distinct location to intranuc lear components.