Unknown,Transcriptomics,Genomics,Proteomics

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Impact of miRNA Levels, Target-Site Complementarity and Cooperativity on ceRNA-Regulated Gene Expression

ABSTRACT: Expression changes of competitive endogenous RNAs (ceRNAs) have been proposed to influence microRNA (miRNA) activity and thereby regulate other transcripts that contain miRNA binding sites. Here, we find that although miRNA levels define the extent of repression, they do not affect the magnitude of the ceRNA expression change required to observe derepression. Canonical 6-nt sites, which typically mediate modest repression, can nonetheless compete for miRNA binding, with potency ~20% of that observed for canonical 8-nt sites. Sites with extensive additional complementarity can be even more potent, but this occurs predominantly through miRNA degradation rather than competition. Cooperative binding of closely spaced sites for different miRNAs can also increase potency. These results provide quantitative insights into the stoichiometric relationship between miRNA and target abundance, target-site spacing and affinity requirements for ceRNA-mediated gene regulation and specify the unusual circumstances in which ceRNA-mediated gene regulation might be observed. Sixty-four mRNA profiles were generated of 1) primary hepatocytes of mice expressing variable levels of a recombinant Adenovirus expressing the transcript of AldolaseA (Ad-AldoA), containing sites matching miR-122, let-7, miR-192, miR-194 or a mutated site (no site) or 2) embryonic stem (ES) cells that were transfected with a Tet-inducible dual-color reporter construct expressing enhanced yellow fluorescent protein (eYFP) and mCherry that contains zero (0s) or three (3s) 8 nt miRNA seed matches for miR-293 or miR-92 in the 3â?² UTR. ES cells were sorted with a FACSAria IIIu flow cytometer into three bins based on their eYFP fluorescence intensity. All samples were sequenced in duplicates by an Illumina HiSeq 2500. Library preparation and sequencing were performed by Fasteris SA (Switzerland) or by the Functional Genomics Centre ZÃ¼rich (FGCZ). Three small RNA profiles or either primary hepatocytes or embryonic stem cells were also generated by Solexa sequencing.

ORGANISM(S): Mus musculus

SUBMITTER: Vikram Agarwal

PROVIDER: E-GEOD-76288 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:The transcription factor ONECUT2 (OC2) is a master transcriptional regulator operating in metastatic castrate-resistant prostate cancer (mCRPC) that suppresses AR activity and promotes neural differentiation and tumor cell survival. OC2 mRNA possesses an unusually long (14,575 nt), evolutionarily conserved 3’-untranslated region (3’-UTR) with many microRNA binding sites, including up to 26 miR-9 sites. This is notable because miR-9 targets many of the same genes regulated by the OC2 protein. Paradoxically, OC2 expression is high in tissues with high miR-9 expression. The length and complex secondary structure of the OC2 mRNA suggests it is a potent master competing endogenous RNA (ceRNA) capable of sequestering miRNAs. Here we describe a novel role for the OC2 3’-UTR in lethal prostate cancer consistent with a function as a ceRNA. A plausible ceRNA network in OC2-driven tumors was constructed computationally then confirmed in prostate cancer cell lines. Genes regulated by the OC2 3’-UTR exhibited high overlap (up to 45%) with genes driven by overexpression of the OC2 protein in the absence of the 3’-UTR, indicating a cooperative functional relationship between the OC2 protein and its 3’-UTR. These overlapping networks suggest an evolutionarily conserved mechanism to reinforce OC2 transcription by protection of OC2-regulated mRNAs from miRNA suppression. Both the protein and the 3’ UTR showed increased Polycomb Repressive Complex activity. Expression of OC2 3’-UTR mRNA alone (without protein) dramatically increased metastatic potential by in vitro assays. Additionally, OC2 3’-UTR increased expression of Aldo-Keto Reductase and UDP-glucuronyl transferase family genes responsible for altering the androgen synthesis pathway. ONECUT2 represents the first described dual-modality transcript that operates as both a key transcription factor driving castration resistant prostate cancer but also as a master ceRNA that promotes and protects the same transcriptional network

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Impact of miRNA Levels, Target-Site Complementarity and Cooperativity on ceRNA-Regulated Gene Expression

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