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.
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 .
Which polymerase transcribes pri-miRNAs?
Which polymerase transcribes pri - miRNAs ?
RNA polymerase II
RNA polymerase II RNAPII