Joint Science Department Seminar


"The Unusual Telomeres of Drosophila"
James M. Mason
Laboratory of Molecular Genetics, National Institute of Environmental Health Sciences
From: 11:00 AM To: 12:00 PM
Tuesday, Mar 29, 2011
Keck Science Center, Burns Lecture Hall
Abstract: Telomeres serve two vital functions in eukaryotes. They distinguish natural chromosome ends from double stranded DNA breaks and thus avoid inappropriate fusions of telomeric sequences. This is generally known as capping. Telomeres also maintain chromosome length by adding DNA to the ends of chromosomes to balance the loss of terminal sequences due to the inability of the replication machinery to completely replicate linear DNA molecules. Most eukaryotes elongate chromosome ends with a special reverse transcriptase, telomerase, that carries a specific RNA template. Although telomerase may have been the mechanism of telomere maintenance of the last common eukaryotic ancestor, it is not the only mechanism used to maintain chromosome length. Drosophila lacks telomerase and the telomeric tandem repeats generated by telomerase. We have identified a mutation in Drosophila that potentiates broken chromosomes lacking a natural telomere. The new chromosome ends are capped, but they lack a telomere-specific DNA sequence and lose material at a rate consistent with incomplete DNA replication. Examination of these new chromosome ends identified non-LTR retrotransposable elements that target chromosome ends. Tandem arrays of these retrotransposons constitute the telomere-specific DNA of Drosophila chromosomes. These results indicate that Drosophila telomeres are epigenetic in that they can form and be maintained in the absence of a specific DNA sequence at the extreme chromosome terminus.
Seminar Registered by: Velda Yount


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