Transposon Regulation: Control of Expression in Drosophila Melanogaster and Consequences of Disregulation in Human Cells

Abstract

Transposons were first discovered as "jumping genes" by Barbara McClintock, who continued to study them in maize through the 1940's and 1950's. Since then, transposons have been shown to make up a large percentage of eukaryotic genomes, including close to half of the human genome, but have been dismissed as simply "junk DNA." Recently, the importance of keeping transposons tightly regulated within the cellular environment has begun to be appreciated; the mechanisms to accomplish this have been studied and the current understanding of pathways governing transposon regulation is discussed within this dissertation. However, recent work presented within the scope of this dissertation in Drosophila melanogaster revealed a previously unknown function for condensin complexes in transposable element regulation. These studies provide a link between pathways governing chromosome pairing and transposon regulation. The potential interplay between these two pathways is intriguing and until now, largely unexplored.Aside from how transposons themselves are regulated, studies into potential roles they may play in the regulation of other protein coding genes within the cell may provide clues into the functionality of these elements within our genome. As a specific example, BRCA1 has a high density of retrotransposon sequences within its primary transcript, and studies of BRCA1 regulation presented within this dissertation has led to the development of a model for a novel gene regulatory mechanism occurring in human cells involving retrotransposons. This mechanism may provide direct relevance to cancer etiology, as retrotransposons have long been known to be misregulated in cancer.As a sum, the work presented within this dissertation extends our knowledge of how transposons are regulated and provides some of the first evidence for their functionality in gene regulatory pathways within human cells.