title: The NF90-NF45 complex functions as a negative regulator in the microRNA processing pathway.
abstract: 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.
authors.affiliation: Laboratory of Molecular Biology, Science Research Center, Kochi Medical School, Kochi 783-8505, Japan. sshuji@kochi-u.ac.jp
authors.forename: Shuji
authors.initials: S
authors.lastname: Sakamoto
authors.forename: Kazuma
authors.initials: K
authors.lastname: Aoki
authors.forename: Takuma
authors.initials: T
authors.lastname: Higuchi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Todaka
authors.forename: Keiko
authors.initials: K
authors.lastname: Morisawa
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Tamaki
authors.forename: Etsuro
authors.initials: E
authors.lastname: Hatano
authors.forename: Atsuki
authors.initials: A
authors.lastname: Fukushima
authors.forename: Taketoshi
authors.initials: T
authors.lastname: Taniguchi
authors.forename: Yasutoshi
authors.initials: Y
authors.lastname: Agata
mesh_terms: 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
chemical_list: 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