Role of transposable elements in heterochromatin and epigenetic control
Role of transposable elements in heterochromatin and epigenetic control
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DOI：
10.1038/nature02651
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发表时间：
2004-07-22
期刊：
影响因子：
64.8
通讯作者：
Martienssen, R
中科院分区：
文献类型：
--
作者：
Lippman, Z;Gendrel, AV;Martienssen, R
异染色质被定义为在间期仍保持浓缩状态且染色较深的染色体物质，而常染色质则会去浓缩。异染色质位于着丝粒和端粒附近，但植物基因组中异染色质的间隙位点（结）很常见，最初是在玉米中被描述的。这些区域是重复的且复制较晚。在果蝇中，异染色质影响基因表达，这种异染色质现象被称为位置效应花斑。果蝇中的位置效应花斑与玉米中由“控制元件”（即转座元件）介导的基因沉默之间的相似性，在一定程度上导致了这样一种观点：异染色质由转座元件组成，并且这些散布在整个基因组中的元件可能调控发育。通过微阵列分析，我们表明拟南芥中的异染色质是由转座元件和相关的串联重复序列决定的，且受染色质重塑ATP酶DDM1（DNA甲基化降低1）的控制。小干扰RNA（siRNAs）与这些序列相对应，表明其在引导DDM1方面的作用。我们还表明转座元件可以表观遗传地调控基因，但只有当插入基因内部或非常接近基因时才可以。这可能解释了DDM1和DNA甲基转移酶MET1对常染色质、印记基因FWA的调控，因为其启动子是由与siRNAs相关的转座元件衍生的串联重复序列提供的。
Heterochromatin has been defined as deeply staining chromosomal material that remains condensed in interphase, whereas euchromatin undergoes de-condensation(1). Heterochromatin is found near centromeres and telomeres, but interstitial sites of heterochromatin ( knobs) are common in plant genomes and were first described in maize(2). These regions are repetitive and late-replicating(3). In Drosophila, heterochromatin influences gene expression, a heterochromatin phenomenon called position effect variegation(4). Similarities between position effect variegation in Drosophila and gene silencing in maize mediated by "controlling elements" ( that is, transposable elements) led in part to the proposal that heterochromatin is composed of transposable elements, and that such elements scattered throughout the genome might regulate development(2). Using microarray analysis, we show that heterochromatin in Arabidopsis is determined by transposable elements and related tandem repeats, under the control of the chromatin remodelling ATPase DDM1 (Decrease in DNA Methylation 1). Small interfering RNAs (siRNAs) correspond to these sequences, suggesting a role in guiding DDM1. We also show that transposable elements can regulate genes epigenetically, but only when inserted within or very close to them. This probably accounts for the regulation by DDM1 and the DNA methyltransferase MET1 of the euchromatic, imprinted gene FWA, as its promoter is provided by transposable-element-derived tandem repeats that are associated with siRNAs.