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1	Site Directed Mutagenesis, Expression and Enzymatic Studies of the 60 kDa Human HIV-TAT 1 Interactive Protein, TIP60 Elangwe, Emilia N 17 July 2009 (has links) Tip60 is a 60 kDa nuclear protein which exists in three isoforms, belongs to the MYST/HAT family of proteins and was discovered after its interaction with the Human HIV-1 Tat. As a nuclear protein, Tip60 can act as a coactivator or repressor. To understand the HAT action of Tip60, two possible catalytic models exist; the ping-pong and the ternary complex formation models. In correlation with the exploration of HAT catalytic action, mutations of a Cys to Ala and a Glu to Gln on Esa1 (yeast homolog of Tip60 and MYST/HAT prototype), was reported to show wild type-like and decreased acetylating properties, respectively. In this work, Tip60 HAT action was explored. In Tip60, the Cys in the active site is important for acetylation of the H4(1-20) substrate and the Glu showed semi loss in acetylating the H4(1-20) peptide substrate. These data highlight a unique mechanism of Tip60 catalysis. Tip60 Site-directed mutagenesis HATs His-tagged Protein Expression HAT assay Post-translational modification Tip60 catalysis Chromatin modification Histones Chromatin MYST family HATs Histone acetylation and HAT inhibitors