Molly Shook

CHARACTERIZATION OF HISTONE ACETYLTRANSFERASES FROM ARABIDOPSIS THALIANA. Molly Shook¹, Keith Earley¹, and Craig Pikaard¹, Biology Department, Washington University, St. Louis, MO¹.

Transcriptionally active chromatin is often associated with highly acetylated lysine residues on N-terminal histone tails. Histone acetyltransferases (HATs) are a class of enzymes that acetylate these lysines, leading to a more relaxed chromatin structure and increased transcription. They have been extensively researched in several species as regulators of gene expression, but their function in plants is not well understood. The Arabidopsis genome encodes twelve HATs classified into four families on the basis of similar sequence motifs. Protein sequence alignments demonstrate significant homology between each of these families and HATs found in other organisms, including the H. sapiens CBP and S. cerevisiae GCN5 proteins. Our enzymatic assays confirm that members of three plant HAT families have histone acetyltransferase activity and reveal their specificities to histone H3 and H4 lysine residues. Additionally, the cellular localization of each HAT was determined through visualization of HAT-YFP fusion proteins with fluorescence microscopy. These characterizations can be useful in studying histone acetylation as a mechanism of transcriptional activation in plants.