Epigenetic regulation of retrotransposons within the nucleolus of Drosophila
Epigenetic regulation of retrotransposons within the nucleolus of Drosophila
复制标题
DOI：
10.1128/mcb.01015-08
复制
发表时间：
2008-10-01
影响因子：
5.3
通讯作者：
Eickbush, Thomas H.
中科院分区：
文献类型：
--
作者：
Eickbush, Danna G.;Ye, Junqiang;Eickbush, Thomas H.
R2逆转录转座元件完全插入到串联组织的28S rRNA基因的保守区域。尽管这些基因的一个子集失活，R2元素在昆虫的核糖体DNA （rDNA）位点上持续存在了数亿年。在这项研究中，研究人员利用先前显示具有活性或非活性R2反转位的果蝇模拟系来控制R2增殖。具有活性反转录转位的细胞系显示出较高的R2转录水平，核运行转录实验表明这是由于R2插入基因的转录增加所致。R2活性系和失活系之间的杂交表明，这种转录控制的一个重要组成部分与rDNA位点相连或靠近rDNA位点，失活亲本的R2转录水平占主导地位。脉冲场凝胶分析表明，基因座内的R2分布决定了R2的活性和失活状态。分子和细胞学分析进一步表明，来自活性系的整个rDNA位点可以被沉默，而有利于来自非活性系的位点。整个rDNA位点的沉默是转座因子大规模表观遗传控制的一个例子，与种在种间杂交中常见的核仁显性具有相同的特征。
R2 retrotransposable elements exclusively insert into a conserved region of the tandemly organized 28S rRNA genes. Despite inactivating a subset of these genes, R2 elements have persisted in the ribosomal DNA ( rDNA) loci of insects for hundreds of millions of years. Controlling R2 proliferation was addressed in this study using lines of Drosophila simulans previously shown to have either active or inactive R2 retrotransposition. Lines with active retrotransposition were shown to have high R2 transcript levels, which nuclear run-on transcription experiments revealed were due to increased transcription of R2-inserted genes. Crosses between R2 active and inactive lines indicated that an important component of this transcriptional control is linked to or near the rDNA locus, with the R2 transcription level of the inactive parent being dominant. Pulsed-field gel analysis suggested that the R2 active and inactive states were determined by R2 distribution within the locus. Molecular and cytological analyses further suggested that the entire rDNA locus from the active line can be silenced in favor of the locus from the inactive line. This silencing of entire rDNA loci represents an example of the large-scale epigenetic control of transposable elements and shares features with the nucleolar dominance frequently seen in interspecies hybrids.