Capturing the dynamic epigenome using single molecule and single cell approaches

点击翻译按钮获取中文摘要

Abstract Our bodies consist of billions of genetically identical cells with the capacity to exhibit distinct phenotypic or epigenetic states. The establishment of epigenetic states, in part, depends on the covalent and reversible modification of DNA packaging proteins called histones. Histone H3 lysine 9 methylation (H3K9me) is associated with transcriptional gene silencing and heterochromatin formation. This process underpins normal centromere and telomere function, transposon silencing and the inactivation of repetitive DNA elements. The loss of heterochromatin in cells is associated with chromosome segregation defects, and genome instability. Our long term goal is to identify and reconstitute heterochromatin dependent protein interactions and capture how these dynamic processes alter heritable gene expression states in single cells and individual lineages. Although histones are partitioned between daughter strands during DNA replication, it remains unclear as to whether the modifications themselves are sufficient to act as carriers of epigenetic memory. The prevailing notion is that a balance of enzymatic activities between proteins that can read, write and erase histone modifications alters the stability and heritability of epigenetic states. Our recent studies have revealed that proteins previously thought to act as histone modifying enzymes proteins play structural or non- enzymatic roles that profoundly impact heterochromatin stability. Using fission yeast, Schizosaccharomyces pombe, as a model system, the major goals of this proposal are 1) to biochemically define and reconstitute heterochromatin dependent protein interactions that are implicated in epigenetic inheritance 2) identify factors that coordinate parental histone transfer with DNA replication to ensure that epigenetic memory is passed on from parental cells to daughter cells following cell division 3) capture the cellular trajectory leading to the establishment of ad hoc or adaptive epigenetic states in response to acute genomic stress. We expect that our studies will identify new regulatory mechanisms that impact heterochromatin assembly and inheritance in addition to discovering how cells leverage these pathways to respond to acute changes in genomic homeostasis. .