Oleic Acid Induces MiR-7 Processing through Remodeling of Pri-MiR-7/Protein Complex

Abstract

MicroRNAs (miRs) play a vital role in governing cell function, with their levels tightly controlled at transcriptional and post-transcriptional levels. Different sets of RNA-binding proteins interact with primary miRs (pri-miRs) and precursor-miR transcripts (pre-miRs), controlling their biogenesis post-transcriptionally. The Hu antigen R (HuR)-mediated binding of Musashi homolog2 (MSI2) to the conserved terminal loop of pri-miR-7 regulates the levels of brain-enriched miR-7 formation in a tissue-specific manner. Here, we show that oleic acid (OA) inhibits the binding of proteins containing RNA recognition motifs (RRM) to the conserved terminal loop of pri-miR-7. Using electrophoretic mobility shift assays in HeLa cell extracts, we show that OA treatment disrupts pre-miR/protein complexes. Furthermore, OA rescues in vitro processing of pri-miR-7, which is otherwise blocked by HuR and MSI2 proteins. On the contrary, pri-miR-16 shows reduced processing in the presence of OA. This indicates that OA may inhibit the binding of other RRM-containing protein/s necessary for miR-16 processing. Finally, we demonstrate that OA induces mature miR-7 production in HeLa cells. Together, our results demonstrate that OA can regulate the processing of pri-miRs by remodeling their protein complexes. This provides a new tool to study RNA processing and a potential lead for small molecules that target the miR-7 biogenesis pathway.

Regulation of transferrin receptor-1 mRNA by the interplay between IRE-binding proteins and miR-7/miR-141 in the 3′-IRE stem–loops

“…4F). Although it is still in the early stages for our understanding of the regulatory mechanisms of individual miRNA expression, it was shown that miR-7 was increased by estrogen (Masuda et al 2012), oleic acid (Kumar et al 2017), and curcumin (Feng et al 2017) in some cancer cells, while miR-141/ 200 expression was induced by oxidative stress such as hydrogen peroxide (Magenta et al 2011;Mateescu et al 2011). It is obvious that the regulation of IRP-IRE interactions by cellular iron status governs the stability of TfR1 mRNA; however, it is conceivable that expression changes in these miRNAs in response to environmental cues and in different tissues ultimately determine the stability of TfR1 mRNA and cellular iron metabolism.…”

Post-transcriptional control of miRNA biogenesis

“…Oleic acid (a natural monounsaturated fatty acid produced by plants and animal cells) inhibits the RNA-binding activity of Musashi RNA-binding protein 2 (MSI2), a negative regulator of pri-mir-7 processing, by binding to its N-terminal RRM (Choudhury et al 2013;Clingman et al 2014). Thus, the action of oleic acid could be used to disrupt the formation of a negative regulatory complex and lead to stimulation of miR-7 biogenesis (Kumar et al 2017). Such strategies could reduce the levels of miR-7 target genes such as the EGFR oncogene, to potentially alleviate its deleterious effects in high-grade glioblastomas, where miR-7 is post-transcriptionally down-regulated (Kefas et al 2008).…”

Acidic extracellular environment affects miRNA expression in tumors in vitro and in vivo

“…Different aspects have to be considered when explaining this discrepancy between in vivo and in vitro results especially for miR‐7. On the one hand, other factors regulating the miR‐7 expression have been described, for instance INF‐γ or oleic acid . The in vitro experiments were performed in the absence of fetal calf serum (FCS) which is different from the situation in vivo , were many cytokines or growth factors are present.…”

“…On the one hand, other factors regulating the miR-7 expression have been described, for instance INF-γ or oleic acid. 48,49 The in vitro experiments were performed in the absence of fetal calf serum (FCS) which is different from the situation in vivo, were many cytokines or growth factors are present. Since it is known that cytokines affect the expression of miRNAs, it was tried to minimize the impact of these factors on the results of the in vitro experiments.…”