Manzano David, Marquardt Sebastian, Jones Alexandra M E, Bäurle Isabel, Liu Fuquan, Dean Caroline
Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom.
Proc Natl Acad Sci U S A. 2009 May 26;106(21):8772-7. doi: 10.1073/pnas.0903444106. Epub 2009 May 13.
The role of RNA metabolism in chromatin silencing is now widely recognized. We have studied the Arabidopsis RNA-binding protein FCA that down-regulates an endogenous floral repressor gene through a chromatin mechanism involving histone demethylase activity. This mechanism needs FCA to interact with an RNA 3' processing/polyadenylation factor (FY/Pfs2p), but the subsequent events leading to chromatin changes are unknown. Here, we show that this FCA-FY interaction is required for general chromatin silencing roles where hairpin transgenes induce DNA methylation of an endogenous gene. We also show 2 conserved RNA processing factors, AtCPSF100 and AtCPSF160, but not FCA, are stably associated with FY in vivo and form a range of different-sized complexes. A hypomorphic fy allele producing a shorter protein, able to provide some FY functions but unable to interact with FCA, reduces abundance of some of the larger MW complexes. Suppressor mutants, which specifically disrupt the FY motif through which FCA interacts, also lacked these larger complexes. Our data support a model whereby FCA, perhaps after recognition of a specific RNA feature, transiently interacts with FY, an integral component of the canonical RNA 3' processing machinery, changing the interactions of the different RNA processing components. These altered interactions would appear to be a necessary step in this RNA-mediated chromatin silencing.
RNA代谢在染色质沉默中的作用现已得到广泛认可。我们研究了拟南芥RNA结合蛋白FCA，它通过一种涉及组蛋白去甲基化酶活性的染色质机制下调一个内源性花抑制基因。这种机制需要FCA与一个RNA 3'加工/聚腺苷酸化因子（FY/Pfs2p）相互作用，但导致染色质变化的后续事件尚不清楚。在这里，我们表明这种FCA-FY相互作用对于发夹转基因诱导内源性基因DNA甲基化的一般染色质沉默作用是必需的。我们还表明，2个保守的RNA加工因子AtCPSF100和AtCPSF160，而不是FCA，在体内与FY稳定相关，并形成一系列不同大小的复合物。一个产生较短蛋白质的功能减弱的fy等位基因，能够提供一些FY功能但不能与FCA相互作用，降低了一些较大分子量复合物的丰度。特异性破坏FCA与之相互作用的FY基序的抑制突变体也缺乏这些较大的复合物。我们的数据支持一个模型，即FCA可能在识别特定RNA特征后，与FY（经典RNA 3'加工机器的一个组成部分）短暂相互作用，改变不同RNA加工成分的相互作用。这些改变的相互作用似乎是这种RNA介导的染色质沉默中的一个必要步骤。
