Histone acetyltransferase is associated with the nuclear matrix

Area of Science:

• Molecular Biology
• Epigenetics
• Cell Biology

Background:

• Dynamic histone acetylation regulates gene transcription.
• Previously identified rapidly acetylated/deacetylated H4 histones associate with transcriptionally active chromatin fragments.
• These fragments are linked to residual nuclear material containing histone deacetylase activity.

Purpose of the Study:

• To investigate the localization of nuclear histone acetyltransferase (HAT) activity.
• To determine the association of HAT and histone deacetylase (HDAC) with the nuclear matrix.
• To explore the role of these enzymes in chromatin-nuclear matrix interactions.

Main Methods:

• Micrococcal nuclease digestion and chromatin solubilization.
• Isolation of nuclear matrices from chicken erythrocytes and trout liver.
• Assay of histone acetyltransferase and deacetylase activities in isolated nuclear fractions.
• In vitro acetylation assays using nuclear skeleton-bound chromatin.

Main Results:

• The majority of nuclear histone acetyltransferase activity resides in the insoluble residual nuclear material.
• Nuclear matrices contain 60-76% of nuclear HAT activity.
• Enzymes associated with the residual nuclear material catalyze reversible histone acetylation in vitro.
• Solubilization of the nuclear matrix releases HAT activity.

Conclusions:

• Histone acetyltransferase and deacetylase activities are associated with the internal nuclear matrix.
• This association suggests a functional role in mediating the dynamic attachment of transcriptionally active chromatin to the nuclear matrix.
• The nuclear matrix may serve as a platform for epigenetic regulation of gene expression.