Selker, EricStorck, William2020-09-242020-09-242020-09-24https://hdl.handle.net/1794/25593DISSERTATION ABSTRACT William K. Storck Doctor of Philosophy Department of Chemistry and Biochemistry March 2020 Title: Characterization of LSD Complex Function, Histone Exchange, and Regulation of a Tryptophan Catabolism Gene Pair in Neurospora crassa Gene expression is regulated by a plethora of factors associated with chromatin, such as histone proteins. DNA can be methylated and histones can be marked with various chemical tags, which can influence expression of underlying DNA. Chromatin is organized into distinct domains: transcriptionally-active euchromatin and transcriptionally-silent heterochromatin. My dissertation involved investigating different aspects of chromatin regulation in the filamentous fungus Neurospora crassa. I examined heterochromatin spreading in Neurospora mutants defective in lysine-specific demethylase 1 (LSD1). Loss of either LSD1 or its associated complex members, PHF1 or BDP-1, results in variable spreading of trimethylation of H3K9 (H3K9me3) and DNA methylation, and this spreading is dependent on DNA methylation, which is typically not involved in H3K9me3 establishment, and on the catalytic activity of the histone deacetylase complex, HCHC. Though there are gene expression changes present in ∆lsd1 strains, these changes do not appear to be driven by spreading H3K9me3 and DNA methylation. Though their relative positioning within chromatin appears to be regulated, histones are not static structures embedded within DNA, but are subject to constant exchange. I characterized a light-inducible histone turnover reporter strain and used it to build a simple protocol for profiling DNA replication-independent histone turnover in Neurospora. I investigated how histone turnover correlates with gene expression, and observed similarities to other models in turnover profiles over genes. I also examined turnover at heterochromatin domains in heterochromatin mutants, which revealed that loss of H3K9me3 or its binder, HP1, or histone deacetylation by HCHC results in turnover increases. Lastly, I investigated the regulation of a pair of genes involved in tryptophan catabolism, kyn-1 and iad-1. I demonstrate that these genes are induced through the exposure of extracellular tryptophan. Though this locus is enriched for the conserved repressive mark, H3K27me3, loss of which does not appear to significantly affect the activity of this locus. Rather, I show that this locus is repressed by the H3K36 methyltransferase, ASH1, and chromatin remodelers, CRF4-1 and CRF6-1. Another H3K36 methyltransferase, SET-2, is required to overcome this repression. This dissertation contains previously unpublished coauthored material.en-USAll Rights Reserved.DNA MethylationEpigeneticsHeterochromatinHistone MethylationElectronic Thesis or Dissertation