Year: 2015
Type: dissertation
Abstract: An essential component of gene regulation is the organization of eukaryotic genomes into functionally and spatially discrete domains. One such domain is the chromocentre, which is a cluster of pericentric heterochromatin enriched in methylated histone H3 (H3K9me3), major satellite repeat DNA, and the histone variant H3.3 specifically deposited by the death-domain- associated protein (DAXX) chaperone. While studies relying on biochemical-based approaches have provided insight into the mechanistic details of the DAXX-dependent chromatin assembly pathway, they have not yielded a comprehensive model of the consequences of this deposition on global chromatin organization. Using electron spectroscopic imaging (ESI), I show that in the absence of DAXX, there is a breakdown in chromocentre structure and a loss of morphological distinction between the repressive histone modification H3K9me3 and chromatin compaction. In addition, I demonstrate that the structural integrity of the nucleolus requires DAXX-dependent heterochromatin organization as its loss causes an increased number of "mini" nucleoli and the dispersal of ribosomal DNA genes. As well, I investigated the role of DAXX in the C2C12 muscle differentiation model and found that concomitant with the formation of terminally differentiated myotubes is the relocalization of DAXX from promyelocytic leukemia nuclear body (PML NBs) to constitutive heterochromatin domains. Taken together, these data reveal that DAXX is a regulator of heterochromatin organization and for the first time, shows the direct consequences of its loss on the global nuclear landscape.
Source: TSpace (University of Toronto)
Author: Lindsy M Rapkin
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2783143086