Autoacetylation of the MYST Lysine Acetyltransferase MOF

The MYST family of histone acetyltransferases (HATs) plays critical roles in diverse cellular processes, such as the epigenetic regulation of gene expression. Lysine autoacetylation of the MYST HATs has received considerable attention recently. Nonetheless, the mechanism and function of the autoacetylation process are not well defined. To better understand the biochemical mechanism of MYST autoacetylation and the impact of autoacetylation on the cognate histone acetylation, we carried out detailed analyses of MOF, a key member of the MYST family. A number of mutant MOF proteins were produced with point mutations at several key residues near the active site of the enzyme. Autoradiography and immunoblotting data showed that mutation of these residues affects the autoacetylation activity and HAT activity of MOF by various degrees demonstrating that MOF activity is highly sensitive to the chemical changes in those residues. We produced MOF protein in the deacetylated form by using a nonspecific lysine deacetylase. Interestingly, both the autoacetylation activity and the histone acetylation activity of the deacetylated MOF was found to be very close to that of wildtype MOF, suggesting that autoacetylation of MOF only marginally modulates the enzymatic activity. Also, we found that the autoacetylation rates of MOF and deacetylated MOF are much slower than the cognate substrate acetylation. Thus autoacetylation does not seem to contribute to the intrinsic enzymatic activity in a significant manner. These data provide new insights into the mechanism and function of MYST HAT autoacetylation. INTRODUCTION Histone acetyltransferases (HATs), also often referred to as protein lysine acetyltransferases (KATs), catalyze the addition of acetyl groups in histone and non-histone proteins (1-6). The acetylation catalyzed by HATs occurs on the epsilon-amino group of specific lysine residues with the cosubstrate acetyl-coenzyme A (acetylCoA, AcCoA) as the acetyl donor. First discovered in nucleosomal histones, protein acetylation is now widely recognized extending far beyond the chromatin realm and orchestrates other diverse biological functions and processes, including cell cycle, cytoskeleton remodeling, chaperones, ribosome, and metabolic pathways (712). In the past decade, significant progress has been made in various aspects of HAT biology, from enzyme kinetics, protein structures, gene regulation, signal transduction, cell development, to disease mechanism and inhibitor development (13-19). Based on the sequence and structural similarities, HATs are grouped into several major http://www.jbc.org/cgi/doi/10.1074/jbc.M112.359356 The latest version is at JBC Papers in Press. Published on August 23, 2012 as Manuscript M112.359356 Copyright 2012 by The American Society for Biochemistry and Molecular Biology, Inc. by gest on N ovem er 8, 2017 hp://w w w .jb.org/ D ow nladed from