The NF90-NF45 Complex Functions as a Negative Regulator in the MicroRNA Processing Pathway
The NF90-NF45 Complex Functions as a Negative Regulator in the MicroRNA Processing Pathway
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DOI：
10.1128/mcb.01836-08
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发表时间：
2009-07-01
影响因子：
5.3
通讯作者：
Agata, Yasutoshi
中科院分区：
文献类型：
--
作者：
Sakamoto, Shuji;Aoki, Kazuma;Agata, Yasutoshi
microRNA（miRNA）加工途径中的正调控机制相对较好地表征，但该途径的负调控在很大程度上是未知的。在这里，我们表明，核因子90（NF 90）和NF 45蛋白质的复合物作为一个负调节器的miRNA生物合成的功能。通过过度表达NF 90和NF 45蛋白，抑制初级miRNA（pri-miRNA）加工成前体miRNA（pre-miRNA），并且大量pri-miRNA在共表达NF 90和NF 45的细胞中积累。用RNA聚合酶II抑制剂α-鹅膏蕈碱处理过表达NF 90和NF 45的细胞，没有减少pri-miRNA的量，这表明pri-miRNA的积累不是由于转录激活。此外，未发现NF 90和NF 45复合物与微处理器复合物相互作用，微处理器复合物是pri-miRNA的加工因子，但发现其结合内源性pri-miRNA。NF 90-NF 45对pri-let-7a的结合活性高于pri-miR-21。值得注意的是，NF 90的消耗导致pri-let-7a的减少和成熟let-7a miRNA的增加，其具有有效的抗增殖活性，并导致转化细胞的生长抑制。这些发现表明NF 90-NF 45复合物与pri-miRNA的结合损害了微处理器复合物对pri-miRNA的接近，导致成熟miRNA产生的减少。
The positive regulatory machinery in the microRNA (miRNA) processing pathway is relatively well characterized, but negative regulation of the pathway is largely unknown. Here we show that a complex of nuclear factor 90 (NF90) and NF45 proteins functions as a negative regulator in miRNA biogenesis. Primary miRNA (pri-miRNA) processing into precursor miRNA (pre-miRNA) was inhibited by overexpression of the NF90 and NF45 proteins, and considerable amounts of pri-miRNAs accumulated in cells coexpressing NF90 and NF45. Treatment of cells overexpressing NF90 and NF45 with an RNA polymerase II inhibitor, alpha-amanitin, did not reduce the amounts of pri-miRNAs, suggesting that the accumulation of pri-miRNAs is not due to transcriptional activation. In addition, the NF90 and NF45 complex was not found to interact with the Microprocessor complex, which is a processing factor of pri-miRNAs, but was found to bind endogenous pri-miRNAs. NF90-NF45 exhibited higher binding activity for pri-let-7a than pri-miR-21. Of note, depletion of NF90 caused a reduction of pri-let-7a and an increase of mature let-7a miRNA, which has a potent antiproliferative activity, and caused growth suppression of transformed cells. These findings suggest that the association of the NF90-NF45 complex with pri-miRNAs impairs access of the Microprocessor complex to the pri-miRNAs, resulting in a reduction of mature miRNA production.