Université Paris Sud, Laboratoire Epigenetique et Cancer, Formation de Recherche en Evolution, Gif-Sur-Yvette, France.
Nat Struct Mol Biol. 2012 Oct;19(10):998-1004. doi: 10.1038/nsmb.2373. Epub 2012 Sep 9.
Argonaute proteins play a major part in transcriptional gene silencing in many organisms, but their role in the nucleus of somatic mammalian cells remains elusive. Here, we have immunopurified human Argonaute-1 and Argonaute-2 (AGO1 and AGO2) chromatin-embedded proteins and found them associated with chromatin modifiers and, notably, with splicing factors. Using the CD44 gene as a model, we show that AGO1 and AGO2 facilitate spliceosome recruitment and modulate RNA polymerase II elongation rate, thereby affecting alternative splicing. Proper AGO1 and AGO2 recruitment to CD44 transcribed regions required the endonuclease Dicer and the chromobox protein HP1γ, and resulted in increased histone H3 lysine 9 methylation on variant exons. Our data thus uncover a new model for the regulation of alternative splicing, in which Argonaute proteins couple RNA polymerase II elongation to chromatin modification.
Argonaute 蛋白在许多生物体的转录基因沉默中起着重要作用，但它们在体细胞哺乳动物细胞核中的作用仍不清楚。在这里，我们已经免疫纯化了人类 Argonaute-1 和 Argonaute-2（AGO1 和 AGO2）与染色质结合的蛋白，并发现它们与染色质修饰物相关，特别是与剪接因子相关。使用 CD44 基因作为模型，我们表明 AGO1 和 AGO2 有助于剪接体的募集，并调节 RNA 聚合酶 II 延伸率，从而影响可变剪接。AGO1 和 AGO2 正确募集到 CD44 转录区域需要内切酶 Dicer 和 chromobox 蛋白 HP1γ，并且导致变体外显子上组蛋白 H3 赖氨酸 9 的甲基化增加。我们的数据因此揭示了一种新的可变剪接调控模型，其中 Argonaute 蛋白将 RNA 聚合酶 II 延伸与染色质修饰联系起来。
