Microscopy studies of metazoan cells have long suggested that the nucleus is a highly structured organelle consisting of multiple, distinct subcompartments and proteinaceous structures. While correlative analyses have generated many hypotheses to explain why such structures may be important for various nuclear processes, efforts to validate these hypothesis functionally have been frustrated by a lack of experimental models and tools. Here, we develop such tools and assays in order to elucidate the function of the nuclear lamina, a compartment that has been suggested to play a role in scaffolding transcriptionally inactive chromatin domains. We demonstrate that the nuclear lamina harbors enzymatic activities that function to both transcriptionally silence large sections of chromatin as well as physically tether them to the inner nuclear membrane (INM). Furthermore, we show that the mechanism by which this tethering occurs is based on particular DNA-sequences, which we propose recruit sequence specific transcription factors, histone deacetylases and other chromatin modifying proteins to create stable domains of epigenetic silencing at the lamina. Additionally, we demonstrate that INM proteins first make contact with these chromatin regions in late anaphase, and suggest this interaction may aid in the reassembly of the nuclear envelope following mitosis. Finally, we identify a developmentally important transcription factor, Ebf1, which is sufficient to reposition a locus from the INM to the nuclear interior, providing the first insight into how a specific lamina-associated region may be regulated during development. Collectively, these studies represent the first rigorous investigation into the processes that connect chromatin organization and transcriptional regulation.
|Commitee:||Holaska, James, McNally, Elizabeth, Staley, Jonathan, Storb, Ursula|
|School:||The University of Chicago|
|Department:||Molecular Genetics and Cell Biology|
|School Location:||United States -- Illinois|
|Source:||DAI-B 72/06, Dissertation Abstracts International|
|Subjects:||Molecular biology, Cellular biology|
|Keywords:||Chromatin structure, Chromosome, DNA sequence, Inner nuclear membrane, Nuclear lamina, Repression|
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