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The enigma of Y chromosome degeneration: TRAM, a novel retrotransposon is preferentially located on the Neo-Y chromosome of Drosophila miranda.

ABSTRACT: We have cloned a novel transposable element from the neo-Y chromosome of Drosophila miranda. The size of the element, designated as TRAM, is 3.452 bp, including on both sides long terminal direct repeats (LTRs) of 372 bp, respectively. The element is flanked by a 5-bp target site duplication, ATATG. The putative primer binding site (PBS) for minus-strand priming is complementary to 18 nucleotides of the 3'-end of tRNA(Trp). Data base screens for DNA sequence identities were negative, apart from the sequence motif of the PBS. The deduced amino acid sequence from the large ORF does not reveal identities described for other transposons. In situ hybridizations with TRAM subclones show a biased distribution in the genome, with a massive accumulation of TRAM in the neo-Y chromosome, while the former homologue, the X2 chromosome is devoid of TRAM sites. The enriched occurrence of the TRAM element at the evolving neo-Y chromosome of D.miranda adds compelling evidence in favor of the view that Y chromosome degeneration is driven by the accumulation of transposable elements.

SUBMITTER: Steinemann M

PROVIDER: S-EPMC1207793 | biostudies-other | 1997 Feb

REPOSITORIES: biostudies-other

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The enigma of Y chromosome degeneration: TRAM, a novel retrotransposon is preferentially located on the Neo-Y chromosome of Drosophila miranda.

Steinemann M M Steinemann S S

Genetics 19970201 2

We have cloned a novel transposable element from the neo-Y chromosome of Drosophila miranda. The size of the element, designated as TRAM, is 3.452 bp, including on both sides long terminal direct repeats (LTRs) of 372 bp, respectively. The element is flanked by a 5-bp target site duplication, ATATG. The putative primer binding site (PBS) for minus-strand priming is complementary to 18 nucleotides of the 3'-end of tRNA(Trp). Data base screens for DNA sequence identities were negative, apart from ...[more]

PMID: 9071582

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Project description:Drosophila X chromosomes are disproportionate sources of duplicated genes, and these duplications are usually the result of retrotransposition of X-linked genes to the autosomes. The excess duplication is thought to be driven by natural selection for two reasons: X chromosomes are inactivated during spermatogenesis, and the derived copies of retroposed duplications tend to be testis expressed. Therefore, autosomal derived copies of retroposed genes provide a mechanism for their X-linked paralogs to "escape" X inactivation. Once these duplications have fixed, they may then be selected for male-specific functions. Throughout the evolution of the Drosophila genus, autosomes have fused with X chromosomes along multiple lineages giving rise to neo-X chromosomes. There has also been excess duplication from the two independent neo-X chromosomes that have been examined--one that occurred prior to the common ancestor of the willistoni species group and another that occurred along the lineage leading to Drosophila pseudoobscura. To determine what role natural selection plays in the evolution of genes duplicated from the D. pseudoobscura neo-X chromosome, we analyzed DNA sequence divergence between paralogs, polymorphism within each copy, and the expression profiles of these duplicated genes. We found that the derived copies of all duplicated genes have elevated nonsynonymous polymorphism, suggesting that they are under relaxed selective constraints. The derived copies also tend to have testis- or male-biased expression profiles regardless of their chromosome of origin. Genes duplicated from the neo-X chromosome appear to be under less constraints than those duplicated from other chromosome arms. We also find more evidence for historical adaptive evolution in genes duplicated from the neo-X chromosome, suggesting that they are under a unique selection regime in which elevated nonsynonymous polymorphism provides a large reservoir of functional variants, some of which are fixed by natural selection.

Dataset Information

The enigma of Y chromosome degeneration: TRAM, a novel retrotransposon is preferentially located on the Neo-Y chromosome of Drosophila miranda.

Publications

The enigma of Y chromosome degeneration: TRAM, a novel retrotransposon is preferentially located on the Neo-Y chromosome of Drosophila miranda.

Similar Datasets

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