An NF90/NF110-mediated feedback amplification loop regulates dicer expression and controls ovarian carcinoma progression

Abstract

Reduced expression of DICER, a key enzyme in the miRNA pathway, is frequently associated with aggressive, invasive disease and poor survival in various malignancies. Regulation of DICER expression is, however, poorly understood. Here, we show that NF90/NF110 facilitates DICER expression by controlling the processing of a miRNA, miR-3173, that is embedded in DICER pre-mRNA. Since miR-3173 in turn targets NF90, a feedback amplification loop controlling DICER expression is established. In a nude mouse model, NF90 overexpression reduced proliferation of ovarian cancer cells and significantly reduced tumor size and metastasis while overexpression of miR-3173 dramatically increased metastasis in a NF90- and DICER-dependent manner. Clinically, low NF90 expression and high miR-3173-3p expression were found to be independent prognostic markers of poor survival in a cohort of ovarian carcinoma patients. These findings suggest that, by facilitating DICER expression, NF90 can act as a suppressor of ovarian carcinoma.

NF90 Modulates Processing of a Subset of Human Pri-miRNAs

“…Following loss of NF90, differential expression analysis (fold change ≥ 1.5 or ≤ 0.667; AdjP-value ≤ 0.05) showed that 212 precursor miRNAs, corresponding to 268 mature miRNAs, were upregulated while 126, corresponding to 149 mature miRNAs, were downregulated ( Figure 1B). MiRNAs that have previously been shown to be modulated by NF90, miR-7-1 (14) and miR3173 (19), were found to be upregulated in HepG2 cells following loss of NF90 ( Figure 1B, red dots).…”

“…Total RNA was extracted from HepG2 cells using TRIzol reagent (Thermo Fisher Scientific) and RNA was treated with DNAse I (Promega) according to the manufacturer's instructions. RNA was used for RT-PCR and modified 5' RLM-RACE as described previously (19). Supplementary Table S3.…”

“…The results obtained confirmed the effects observed by miRNA profiling (Figure 1B, C). In addition, RNA was extracted from cells transfected with an independent non-targeting siRNA (Scr#2) and an NF90-targeting siRNA (NF90#2) that has been described previously (19) (Figure 1A, lower panel). Quantification of miRNAs 3173-3p, -186-5p, -1273c and -3189-3p in biological triplicate samples ( Figure 1C, lower panels) showed similar results to those obtained in Figure 1C upper panel, and also validated the results obtained by small RNA-seq.…”

“…Like terminal loop binding RBPs, binding of NF90/NF45 or ADAR1,2 has thus far been demonstrated for a very limited number of pri-miRNAs. NF90 has been shown to associate with pri-miR-7-1, prilet-7A and pri-miR-3173 in human cells (14,15,19).…”

“…Binding of NF90 prevented cropping of pri-miR-3173 by Microprocessor and promoted splicing of the intron, thereby facilitating expression of DICER. By modulating DICER expression, NF90 was found to be an independent prognostic marker of ovarian carcinoma progression (19). Levels of NF90 are known to be elevated in hepatocellular carcinoma (HCC) and the effect of NF90 on processing of pri-miR-7-1 contributes to cellular proliferation in HCC models (14,20).…”