The ends of eukaryotic chromosomes, called telomeres, perform several vital functions. One function is self-maintenance; because loss of DNA from the terminus is inherent in replication, this loss must be counterbalanced by addition of telomeric DNA to the terminus. The long- term goal of the research proposed here is to understand the structure of Drosophila telomeres, how they are maintained, and how they function. It appears that Drosophila telomeres are maintained by a novel mechanism involving the occasional transposition to the terminus of specialized families of non-LTR retrotransposons. Non-LTR retrotransposons, also called LINEs, are a class of mobile elements which is ubiquitous among metazoans and has been implicated in causing mutations in man. Two families of telomere-associated LINEs, HeT-A and TART, have been found in Drosophila. A long-term objective of this project is to determine the basis for the unusual transpositional specificity of these elements.
One specific aim proposed in this application is to show that HeT-A and TART elements are at the termini of Drosophila chromosomes by identifying terminal DNA fragments hybridizing with DNA probes for these elements.
A second aim i s to survey the number, DNA sequence organization, and chromosomal locations of TART elements in D. melanogaster and other Drosophila species. This will be accomplished by genomic Southern blot analysis, in situ hybridization, and DNA cloning.
A third aim i s to characterize the expression of TART in D. melanogaster. The transcription unit and promoter will be mapped. The tissues and developmental stages in which the transcription and translation products of TART accumulate will also be determined.
The fourth aim i s to reintroduce a cloned TART element into the germline of D. melanogaster and show that it will transpose to a telomere. This would provide an in vivo transposition assay for future in vitro mutagenesis experiments.
|Maxwell, Patrick H; Belote, John M; Levis, Robert W (2008) Developmental and tissue-specific accumulation pattern for the Drosophila melanogaster TART ORF1 protein. Gene 415:32-9|
|Maxwell, Patrick H; Belote, John M; Levis, Robert W (2006) Identification of multiple transcription initiation, polyadenylation, and splice sites in the Drosophila melanogaster TART family of telomeric retrotransposons. Nucleic Acids Res 34:5498-507|
|Sheen, F M; Levis, R W (1994) Transposition of the LINE-like retrotransposon TART to Drosophila chromosome termini. Proc Natl Acad Sci U S A 91:12510-4|
|Levis, R W (1993) Drosophila melanogaster does not share the telomeric repeat sequence of another invertebrate, Ascaris lumbricoides. Mol Gen Genet 236:440-2|
|Levis, R W; Ganesan, R; Houtchens, K et al. (1993) Transposons in place of telomeric repeats at a Drosophila telomere. Cell 75:1083-93|
|Biessmann, H; Valgeirsdottir, K; Lofsky, A et al. (1992) HeT-A, a transposable element specifically involved in ""healing"" broken chromosome ends in Drosophila melanogaster. Mol Cell Biol 12:3910-8|
|Runkel, N S; Moody, F G; Smith, G S et al. (1991) The role of the gut in the development of sepsis in acute pancreatitis. J Surg Res 51:18-23|
|Levis, R W (1989) Viable deletions of a telomere from a Drosophila chromosome. Cell 58:791-801|