Investigating SWR1 Recruitment in the Maintenance of the epigenomic H2A.Z landscape Público

Abstract

H2A.Z is a histone variant which is essential for embryonic development and environmental response across eukaryotes. H2A.Z  has a dual role in transcriptional regulation of genes; transcription start site (TSS)-proximal H2A.Z is positively associated with transcription, while gene body H2A.Z is negatively associated with transcription. In plants, H2A.Z is found at actively transcribed genes in euchromatin, at facultatively repressed responsive genes, while H2A.Z  is absent from gene poor constitutive heterochromatin. How these distinct profiles of H2A.Z are maintained in relation to deposition machinery the SWI2/SNF2-Related1 (SWR1) complex and the interactor, Methyl-CpG-Binding Domain-containing protein 9 (MBD9) is unclear. Using RNA-Seq and ChIP-Seq in Arabidopsis thaliana, we examined the localization of H2A.Z, the SWR1 catalytic component PIE1, and MBD9 under steady-state conditions, simulated stress, and after ectopic localization of SWR1 to constitutive heterochromatin. In Chapter 2, we demonstrate that normally, facultatively repressed genes have the most H2A.Z yet have the least occupancy of SWR1 and the interacting protein MBD9. Upon transcriptional activation, SWR1 moves to deposit and maintain H2A.Z at these responsive genes. MBD9 also moves to these genes, but it is not necessary for SWR1 recruitment or a proper transcriptional response to stimulus. In Chapter 3, we show that in SWR1 mutants there is ectopic accumulation of H2A.Z at constitutively repressed regions. Ectopic localization of SWR1 to these regions utilizing a transgenic methyl-CpG binding MBD9 mutant results in a partial rescue of normal H2A.Z levels, showing that MBD9 is sufficient to target SWR1 to these regions. Collectively, this work expands our understanding of the influence of H2A.Z and its regulatory network on transcriptional regulation in eukaryotes.

Table of Contents

Chapter 1: 1

Introduction

Chapter 2: 17

SWR1 is recruited to activated ABA response genes to maintain gene body H2A.Z in Arabidopsis thaliana

Chapter 3: 66

SWR1 remodeler activity limits ectopic H2A.Z accumulation at constitutive heterochromatin in Arabidopsis

Chapter 4: 89

Discussion

About this Dissertation

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School	Laney Graduate School
Department	Biological and Biomedical Sciences
Subfield / Discipline	Genetics and Molecular Biology
Degree	Ph.D.
Submission	Dissertation
Language	English
Research Field	Biology, Genetics Biology, Molecular Biology, Botany
Palabra Clave	epigenetics facultative heterochromatin environmental response SWR1 Arabidopsis thaliana PIE1 constitutive heterochromatin H2A.Z MBD9 Abscisic Acid chromatin remodeler histone variant SRCAP
Committee Chair / Thesis Advisor	Roger Deal, Emory University
Committee Members	Jie Jiang, Emory University Anita Corbett, Emory University William Kelly, Emory University Leila Rieder, Emory University

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