BACKGROUND Dosage compensation in Drosophila is the epigenetic process by which the expression of genes located on the single X-chromosome of males is elevated to equal the expression of X-linked genes in females where there are two copies of the X-chromosome. While epigenetic mechanisms are hypothesized to have evolved originally to silence transposable elements, a connection between transposable elements and the evolution of dosage compensation has yet to be demonstrated. RESULTS We show that transcription of the Drosophila melanogaster copia LTR (long terminal repeat) retrotransposon is significantly down regulated when in the hemizygous state. DNA digestion and chromatin immunoprecipitation (ChIP) analyses demonstrate that this down regulation is associated with changes in chromatin structure mediated by the histone acetyltransferase, MOF. MOF has previously been shown to play a central role in the Drosophila dosage compensation complex by binding to the hemizygous X-chromosome in males. CONCLUSION Our results are consistent with the hypothesis that MOF originally functioned to silence retrotransposons and, over evolutionary time, was co-opted to play an essential role in dosage compensation in Drosophila.

中文翻译：

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LTR 逆转录转座子和果蝇剂量补偿的演变。

背景 果蝇中的剂量补偿是表观遗传过程，通过该过程，位于雄性单个 X 染色体上的基因表达升高至与具有两个 X 染色体拷贝的雌性中 X 连锁基因的表达相等。虽然假设表观遗传机制最初是为了使转座元件沉默而进化的，但转座元件与剂量补偿进化之间的联系尚未得到证实。结果我们表明，当处于半合子状态时，黑腹果蝇 copia LTR（长末端重复序列）逆转录转座子的转录显着下调。DNA 消化和染色质免疫沉淀 (ChIP) 分析表明，这种下调与组蛋白乙酰转移酶 MOF 介导的染色质结构变化有关。MOF 先前已被证明通过与雄性半合子 X 染色体结合，在果蝇剂量补偿复合物中发挥核心作用。结论 我们的结果与 MOF 最初的功能是使逆转录转座子沉默的假设一致，并且随着进化时间的推移，被选择在果蝇的剂量补偿中发挥重要作用。