Toleman Clifford A, Paterson Andrew J, Kudlow Jeffrey E
Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, University of Alabama, Birmingham, 35294-0012, USA.
J Biol Chem. 2006 Feb 17;281(7):3918-25. doi: 10.1074/jbc.M510485200. Epub 2005 Dec 15.
Nuclear cytoplasmic O-GlcNAcase and acetyltransferase (NCOAT) is a bifunctional enzyme with both glycoside hydrolase and alkyltransferase activity. Its O-GlcNAcase active site lies in the N terminus of the enzyme and its histone acetyltransferase (HAT) domain lies in the C terminus. Whereas the HAT domain of the enzyme is catalytically and structurally similar to other acetyltransferases across subfamilies, NCOAT has a motif resembling a zinc finger-like domain unique to the MYST family of HATs. Among the MYST family, this zinc finger, or zinc finger-like domain, is responsible for making contacts with the histone tails within nucleosomes for the HAT to catalyze its respective reaction. Here, we show that NCOAT has the ability to directly associate with both an acetylated and unacetylated histone H4 tail in vitro, and a potential zinc finger-like motif found in NCOAT is implicated in this nucleosomal contact, and is necessary for fully efficient enzymatic activity. Subsequent to the catalysis of acetyltransfer to lysine 8 of histone H4 for the enzyme, however, the substrate is released and NCOAT can no longer bind H4 in our assays. Furthermore, this finger domain by itself is sufficient to bind histone H4.
核质O-连接N-乙酰葡糖胺酶和乙酰转移酶（NCOAT）是一种具有糖苷水解酶和烷基转移酶活性的双功能酶。其O-连接N-乙酰葡糖胺酶活性位点位于酶的N端，其组蛋白乙酰转移酶（HAT）结构域位于C端。虽然该酶的HAT结构域在催化和结构上与其他亚家族的乙酰转移酶相似，但NCOAT有一个类似于HAT的MYST家族特有的锌指样结构域的基序。在MYST家族中，这个锌指或锌指样结构域负责与核小体内的组蛋白尾巴接触，以便HAT催化其各自的反应。在这里，我们表明NCOAT在体外具有直接与乙酰化和未乙酰化的组蛋白H4尾巴结合的能力，并且在NCOAT中发现的一个潜在的锌指样基序与这种核小体接触有关，并且对于完全有效的酶活性是必需的。然而，在该酶将乙酰基转移到组蛋白H4的赖氨酸8之后，底物被释放，并且在我们的实验中NCOAT不再能结合H4。此外，这个指状结构域本身就足以结合组蛋白H4。
