Control of transposon activity by a histone H3K4 demethylase in rice
Control of transposon activity by a histone H3K4 demethylase in rice
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水稻中组蛋白 H3K4 去甲基化酶对转座子活性的控制
DOI：
10.1073/pnas.1217020110
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发表时间：
2013-01-29
影响因子：
11.1
通讯作者：
Cao, Xiaofeng
中科院分区：
文献类型：
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作者：
Cui, Xiekui;Jin, Ping;Cao, Xiaofeng
转座因子（te）普遍存在于植物基因组中，通常占核DNA的重要部分。例如，大约40%的水稻基因组由te组成，其中许多是反转录转座子，包括14%的LTR-和1%的非LTR反转录转座子。尽管TE分布广泛且数量丰富，但很少有TE被发现是转位的，这表明TE的活性可能受到宿主基因组的严格控制，以尽量减少与主动转位相关的潜在诱变效应。与这一观点一致的是，越来越多的证据表明，表观遗传沉默途径，如DNA甲基化；RNA干扰和H3K9me2共同作用，在转录和转录后水平抑制TE活性。然而，目前尚不清楚与主动转录相关的组蛋白修饰的去除是否也与TE沉默有关。在这里，我们发现水稻蛋白JMJ703是te沉默所需的活性h3k4特异性去甲基化酶。JMJ703活性受损导致H3K4me3水平升高，许多内源性基因调控错误，以及两个非ltr反转录转座子家族的转座再激活。有趣的是，JMJ703的缺失并不影响先前发现的被其他表观遗传途径沉默的TEs（如Tos17）。这些结果表明，去除活性组蛋白修饰参与TE沉默，TE的不同亚群可能受到不同表观遗传途径的调节。
Transposable elements (TEs) are ubiquitously present in plant genomes and often account for significant fractions of the nuclear DNA. For example, roughly 40% of the rice genome consists of TEs, many of which are retrotransposons, including 14% LTR- and similar to 1% non-LTR retrotransposons. Despite their wide distribution and abundance, very few TEs have been found to be transpositional, indicating that TE activities may be tightly controlled by the host genome to minimize the potentially mutagenic effects associated with active transposition. Consistent with this notion, a growing body of evidence suggests that epigenetic silencing pathways such as DNA methylation; RNA interference, and H3K9me2 function collectively to repress TE activity at the transcriptional and posttranscriptional levels. It is not yet clear, however, whether the removal of histone modifications associated with active transcription is also involved in TE silencing. Here, we show that the rice protein JMJ703 is an active H3K4-specific demethylase required for TEs silencing. Impaired JMJ703 activity led to elevated levels of H3K4me3, the misregulation of numerous endogenous genes, and the transpositional reactivation of two families of non-LTR retrotransposons. interestingly, loss of JMJ703 did not affect TEs (such as Tos17) previously found to be silenced by other epigenetic pathways. These results indicate that the removal of active histone modifications is involved in TE silencing and that different subsets of TEs may be regulated by distinct epigenetic pathways.