The NF90-NF45 complex functions as a negative regulator in the microRNA processing pathway.
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.
Sakamoto
Shuji
S
Laboratory of Molecular Biology, Science Research Center, Kochi Medical School, Kochi 783-8505, Japan. sshuji@kochi-u.ac.jp
Aoki
Kazuma
K
Higuchi
Takuma
T
Todaka
Hiroshi
H
Morisawa
Keiko
K
Tamaki
Nobuyuki
N
Hatano
Etsuro
E
Fukushima
Atsuki
A
Taniguchi
Taketoshi
T
Agata
Yasutoshi
Y
D002460:Cell Line; D006801:Humans; D035683:MicroRNAs / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes / Q000378:metabolism; D051903:Nuclear Factor 45 Protein / Q000235:genetics / Q000378:metabolism*; D050779:Nuclear Factor 90 Proteins / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D034622:RNA Interference; D012322:RNA Precursors / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D043244:Ribonuclease III / Q000235:genetics / Q000378:metabolism
C474043:DGCR8 protein, human; D035683:MicroRNAs; D046912:Multiprotein Complexes; D051903:Nuclear Factor 45 Protein; D050779:Nuclear Factor 90 Proteins; D011506:Proteins; D012322:RNA Precursors; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; C517918:DROSHA protein, human; D043244:Ribonuclease III