What function do HAT and HDAC perform in the chromatin-modifying process?

Question

Quizplus · Accepted Answer

HAT (histone acetyltransferase) adds acetyl groups to the lysine residues of histone proteins, relaxing the chromatin structure and making genes more accessible for transcription. This activation of genes is performed by HAT. 
HDAC (histone deacetylase) removes acetyl groups from the lysine residues of histone proteins, resulting in a more compact chromatin structure which represses gene expression. So, HDAC represses the gene. Therefore, both HAT and HDAC work together to regulate gene expression, but in opposite ways.

What Function Do HAT and HDAC Perform in the Chromatin-Modifying