Transcription factor networks and chromatin remodeler function in gene regulation on the eukaryotic genome
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Numerous events – from histone modification and transcription factor binding to gene expression – take place on eukaryotic chromatin, while cells are constantly exposed to dynamic stimuli ranging from spatial and temporal cues to environmental and extracellular signals. The cell’s ability to respond and adjust accordingly is directly related to cell fitness and viability. With the advent of next-generation sequencing, investigating these events has been enabled at nucleotide resolution but across the entire genome. In this dissertation, I investigate changes on eukaryotic genomes including yeast and human, which are triggered by stress and by loss of a protein of interest, by analyzing genomics data generated mainly through next-generation sequencing. In Chapter 1, I determine how yeast cells achieve transcriptional reprogramming in response to heat stress by first identifying the complete set of transcription factors that are essential for heat stress conditions. This is further explored by identifying both the target loci bound by the transcription factors under conditions of heat-stress, as well as the genes that require the function of the transcription factor for normal transcriptional response to heat stress. In Chapter 2, I study a chromatin remodeling factor, CHD1 (Chromodomain Helicase DNA binding protein 1) with regard to two aspects: first, what factors provide specificity for Chd1 positioning on chromatin, by examining the role of proteins that physically or genetically interact with Chd1, and second, what is the relationship of Chd1 with the hallmark of chromatin modifications, histone H3 tri-methylation at Lys 4 and Lys 36, by investigating changes in these histone methylation marks in the absence of Chd1. Additionally, I show a novel functional link between Chd1 and RNA splicing through analysis of intron retention in transcripts produced in the Chd1 mutant. Lastly, I investigate Chd1 role in human glioblastoma cell line by generating a Chd1 knock-out via the CRISPR/Cas9 genome editing system. Taken together, the work presented in this dissertation provides novel approaches, discoveries, and intriguing insights into how eukaryotic chromatin experiences dynamic alterations in response to various perturbations on a genome-wide scale.