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Modifiers of P-element-dependent silencing in Drosophila melanogaster. Open Access


Other title
gene regulation
cubitus interruptus
p-element dependent silencing
position effect variegation
Type of item
Degree grantor
University of Alberta
Author or creator
McCracken, Allen TM
Supervisor and department
Locke, John (Biological Sciences)
Examining committee member and department
Honda, Barry (Biochemistry and Molecular Biology, SFU)
Nargang, Frank (Biological Sciences)
Campbell, Shelagh (Biological Sciences)
Wevrick, Rachel (Medical genetics)
King-Jones, Kirst (Biological Sciences)
Locke, John (Biological Sciences)
Department of Biological Sciences
Molecular Biology and Genetics
Date accepted
Graduation date
Doctor of Philosophy
Degree level
If all cells in a multicellular organism contain exactly the same genetic information, the question arises of how tissue types with distinct gene expression profiles are formed and maintained over the life of the organism. These different temporal and spatial gene expression patterns are thought to be built by activating and repressing proteins and RNAs to create self-perpetuating chromatin states. Identifying these components is the first and fundamental step in understanding this type of control of gene expression, and is the focus of this thesis. My model system centers on P{lacW}ciDplac , a white (w+) transgene insert on chromosome 4 of Drosophila melanogaster. P{lacW}ciDplac is a previously characterized enhancer trap of ciD that should be sensitive to many of the proteins that regulate ci during development. Normally, the white gene within P{lacW}ciDplac is expressed throughout the adult eye and presents a uniform red eye phenotype. However, the presence of other P elements results in stochastic silencing of the w+ of this transgene and a variegated phenotype in a process called P element dependent silencing (PDS). A derivative allele of P{lacW}ciDplac was isolated, called E1, that contained a distal gypsy element insertion. This allele variegates in the absence of other P elements, and the variegating phenotype can be suppressed by and enhanced by modifiers of wm4 in a manner similar to heterochromatic Position Effect Variegation (hPEV). I performed a genetic screen formodifiers of E1 variegation and isolated mutations that fell into complementation groups on both the second and third chromosomes. I identified 5 of these groups as: TAF4, a general transcription factor; cg, an already characterized regulator of ci; ash1 and trx, known regulators of homeotic genes not previously shown to act at ci; and CG8878, a putative protein kinase of unknown specificity. I also isolated a complementation group that was too weak in phenotype to accurately map via recombination and several singles, which were not pursued farther. I chose to investigate the alleles of ash1, trx, and CG8878. This thesis describes their generation, isolation and further characterization.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
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