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The promoter of the heterochromatic Drosophila telomeric retrotransposon, HeT-A, is active when moved into euchromatic locations.

ABSTRACT: The Drosophila telomeric retrotransposon, HeT-A, is found only in heterochromatin; therefore, its promoter must function in this chromatin environment. Studies of position effect variegation suggest that promoters of heterochromatic genes are very different from euchromatic promoters, but this idea has not been tested with isolated promoter sequences. The HeT-A promoter is the first heterochromatin promoter to be isolated and it is of interest to investigate its activity when removed from telomeric heterochromatin. This promoter was initially characterized by testing reporter constructs in transient transfection of cultured cells, an environment that may approximate its endogenous heterochromatin. We now report P-element-mediated transpositions of these constructs, testing the function of different parts of the putative promoter in euchromatin. Expression of endogenous HeT-A RNA shows marked developmental regulation and accumulates preferentially in replicating diploid tissues. HeT-A promoter constructs are active in all euchromatic locations tested and some display aspects of endogenous HeT-A stage- and cell-type expression programs. The activity of each promoter construct in euchromatic locations is also generally consistent with its activity in the transient transfection tests; a possibly significant exception is one sequence segment that appreciably enhanced activity in transient transfection but repressed promoter activity in euchromatin.

SUBMITTER: George JA

PROVIDER: S-EPMC1462444 | biostudies-other | 2003 Feb

REPOSITORIES: biostudies-other

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The promoter of the heterochromatic Drosophila telomeric retrotransposon, HeT-A, is active when moved into euchromatic locations.

George Janet A JA Pardue Mary-Lou ML

Genetics 20030201 2

The Drosophila telomeric retrotransposon, HeT-A, is found only in heterochromatin; therefore, its promoter must function in this chromatin environment. Studies of position effect variegation suggest that promoters of heterochromatic genes are very different from euchromatic promoters, but this idea has not been tested with isolated promoter sequences. The HeT-A promoter is the first heterochromatin promoter to be isolated and it is of interest to investigate its activity when removed from telome ...[more]

PMID: 12618401

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Project description:BACKGROUND:The potential adaptive significance of transposable elements (TEs) to the host genomes in which they reside is a topic that has been hotly debated by molecular evolutionists for more than two decades. Recent genomic analyses have demonstrated that TE fragments are associated with functional genes in plants and animals. These findings suggest that TEs may contribute significantly to gene evolution. RESULTS:We have analyzed two transposable elements associated with genes in the sequenced Drosophila melanogaster y; cn bw sp strain. A fragment of the Antonia long terminal repeat (LTR) retrotransposon is present in the intron of Chitinase 3 (Cht3), a gene located within the constitutive heterochromatin of chromosome 2L. Within the euchromatin of chromosome 2R a full-length Burdock LTR retrotransposon is located immediately 3' to cathD, a gene encoding cathepsin D. We tested for the presence of these two TE/gene associations in strains representing 12 geographically diverse populations of D. melanogaster. While the cathD insertion variant was detected only in the sequenced y; cn bw sp strain, the insertion variant present in the heterochromatic Cht3 gene was found to be fixed throughout twelve D. melanogaster populations and in a D. mauritiana strain suggesting that it maybe of adaptive significance. To further test this hypothesis, we sequenced a 685bp region spanning the LTR fragment in the intron of Cht3 in strains representative of the two sibling species D. melanogaster and D. mauritiana (approximately 2.7 million years divergent). The level of sequence divergence between the two species within this region was significantly lower than expected from the neutral substitution rate and lower than the divergence observed between a randomly selected intron of the Drosophila Alcohol dehydrogenase gene (Adh). CONCLUSIONS:Our results suggest that a 359 bp fragment of an Antonia retrotransposon (complete LTR is 659 bp) located within the intron of the Drosophila melanogaster Cht3 gene is of adaptive evolutionary significance. Our results are consistent with previous suggestions that the presence of TEs in constitutive heterochromatin may be of significance to the expression of heterochromatic genes.

Dataset Information

The promoter of the heterochromatic Drosophila telomeric retrotransposon, HeT-A, is active when moved into euchromatic locations.

Publications

The promoter of the heterochromatic Drosophila telomeric retrotransposon, HeT-A, is active when moved into euchromatic locations.

Similar Datasets

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