UNRAVELING THE FUNCTIONAL MOTIFS OF THE YAN ENHANCER IN DROSOPHILA MELANOGASTER
Open Access
- Author:
- Ramos, Edward
- Graduate Program:
- Genetics
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- March 31, 2003
- Committee Members:
- Zhi Chun Lai, Committee Chair/Co-Chair
Andrew G Clark, Committee Member
Stephen Wade Schaeffer, Committee Member
David Scott Gilmour, Committee Member - Keywords:
- Drosphila
Yan
Module
Enhancer
Gene Regulation - Abstract:
- The organization of eukaryotic genomes can be divided primarily into two regions, those areas that are transcribed and those that regulate transcription. This thesis focuses on improving our understanding of cis-regulatory modules and how they direct transcription. To address this issue we used the Drosophila melanogaster yan gene as our model. The yan gene encodes a general inhibitor of differentiation and proliferation and is expressed dynamically throughout Drosophila development including oogenesis, embryogenesis and the larval central nervous system (CNS) and eye imaginal disc. We were interested in identifying module elements required for these various stages of expression. In this work we describe analysis of a 20 Kb genomic region surrounding the first exon of the yan gene. We show that discrete parts of this genomic region are responsible for specific subportions of the Yan protein expression pattern. In particular, we isolated a 122 bp fragment that is sufficient to specify yan expression within the developing eye. In this eye-specific enhancer we identified a number of elements critical to directing yan expression including a boundary element associated with insulator activity. One such regulatory element requires Su(H), a component of the Notch pathway, for gene transcription. Experimental data also demonstrated that this activation by the Notch pathway can be negatively modulated by receptor tyrosine kinase (RTK) signaling. Pointed, a nuclear target of the RTK pathway, is able to directly bind to the yan enhancer and compete with Su(H) for DNA binding. This is one of the first instances where these two pathways have been shown to interact directly in an antagonistic manner. In summary, this work not only describes the various genomic components necessary for Yan expression throughout development but also provides a mechanism for regulation of yan transcription during eye development.