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Mechanism of deposition and functional characterization of the histone variant H2A.Z in Saccharomyces cerevisiae

University of British Columbia

Eukaryotic DNA is packaged into the cell nucleus together with histones and other proteins as a complex called chromatin. The dynamic structure of chromatin is crucial for genome regulation and is created by a variety of mechanisms including post-translational modifications, ATP-dependent remodeling, and replacement by histone variants. My dissertation investigates the structure and function of central players in the biology of histone H2A.Z, an important and yet enigmatic variant of H2A. Unlike H2A, which is deposited randomly in the genome, H2A.Z is deposited to specific locations by its dedicated ATP-dependent complex SWR1-C. One subunit that belongs to SWR1-C is Yaf9, which contains the conserved yet largely unexplored YEATS domain. Here, I established the conservation of YEATS domain function from yeast to human. I determined that the three-dimensional structure of the Yaf9 YEATS domain from Saccharyomyces cerevisiae was highly similar to that of the histone chaperone Asf1, a similarity that extended to an ability of Yaf9 to bind histones H3 and H4 in vitro. In addition, I found that the Yaf9 YEATS domain was required for H2A.Z deposition at specific promoters. Focusing on the histone variant itself, I explored the precise features required for H2A.Z to function and specify its unique identity from canonical H2A. I specifically studied the C-terminal docking domain, an area of significant structural and sequence variation between H2A.Z and H2A. I determined that the last 20 amino acids of H2A.Z was required for its chromatin-anchoring ability and functions in vivo, even though it was not required for SWR1-C interaction. Furthermore, I demonstrated that M6, a region in the docking domain that diverged considerably from H2A, was required but not sufficient for H2A.Z–specific functions, including binding to SWR1-C. Finally, I found that the M6 region was both required and sufficient for binding to the H2A.Z-specific histone chaperone Chz1. In summary, my dissertation contributes to our understanding of the structure and function of the Yaf9 YEATS domain in the context of H2A.Z deposition, as well as the distinct regions of the H2A.Z C-terminal docking domain that are either required for its function or confer its uniqueness.

Text

2012-09-28

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/43291

Genetics

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/