ABSTRACT: Endogenous miRNA and target concentrations determine susceptibility to potential ceRNA competition, based on hierarchical binding affinities (small RNA)
Project description:Endogenous miRNA and target concentrations determine susceptibility to potential ceRNA competition, based on hierarchical binding affinities
Project description:Endogenous miRNA and target concentrations determine susceptibility to potential ceRNA competition, based on hierarchical binding affinities (mRNA)
Project description:Endogenous miRNA and target concentrations determine susceptibility to potential ceRNA competition, based on hierarchical binding affinities (iCLIP)
Project description:Target competition (ceRNA crosstalk) within miRNA-regulated gene networks has been proposed to influence biological systems. To assess target competition, we characterize and quantitate miRNA networks in two cell types. Argonaute iCLIP reveals that hierarchical binding of high to low affinity miRNA targets is a key characteristic of in vivo activity. Quantification of cellular miRNA and mRNA/ncRNA target pool levels indicates that miRNA-Target pool ratios and an affinity partitioned target pool accurately predict in vivo Ago binding profiles and miRNA susceptibility to target competition. Using single-cell reporters, we directly test predictions and estimate ~3,000 additional high affinity target sites can affect active miRNA families with low endogenous miRNA-Target ratios, such as miR-92/25. In contrast, the highly expressed miR-294 and let-7 families are not susceptible to increases of nearly 10,000 sites. These results show differential susceptibility based on endogenous miRNA-Target pool ratios and provide a physiological context for ceRNA competition in vivo.
Project description:Target competition (ceRNA crosstalk) within miRNA-regulated gene networks has been proposed to influence biological systems. To assess target competition, we characterize and quantitate miRNA networks in two cell types. Argonaute iCLIP reveals that hierarchical binding of high to low affinity miRNA targets is a key characteristic of in vivo activity. Quantification of cellular miRNA and mRNA/ncRNA target pool levels indicates that miRNA-Target pool ratios and an affinity partitioned target pool accurately predict in vivo Ago binding profiles and miRNA susceptibility to target competition. Using single-cell reporters, we directly test predictions and estimate ~3,000 additional high affinity target sites can affect active miRNA families with low endogenous miRNA-Target ratios, such as miR-92/25. In contrast, the highly expressed miR-294 and let-7 families are not susceptible to increases of nearly 10,000 sites. These results show differential susceptibility based on endogenous miRNA-Target pool ratios and provide a physiological context for ceRNA competition in vivo.
Project description:Target competition (ceRNA crosstalk) within miRNA-regulated gene networks has been proposed to influence biological systems. To assess target competition, we characterize and quantitate miRNA networks in two cell types. Argonaute iCLIP reveals that hierarchical binding of high to low affinity miRNA targets is a key characteristic of in vivo activity. Quantification of cellular miRNA and mRNA/ncRNA target pool levels indicates that miRNA-Target pool ratios and an affinity partitioned target pool accurately predict in vivo Ago binding profiles and miRNA susceptibility to target competition. Using single-cell reporters, we directly test predictions and estimate ~3,000 additional high affinity target sites can affect active miRNA families with low endogenous miRNA-Target ratios, such as miR-92/25. In contrast, the highly expressed miR-294 and let-7 families are not susceptible to increases of nearly 10,000 sites. These results show differential susceptibility based on endogenous miRNA-Target pool ratios and provide a physiological context for ceRNA competition in vivo.
Project description: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 3� 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 Zürich (FGCZ). Three small RNA profiles or either primary hepatocytes or embryonic stem cells were also generated by Solexa sequencing.
Project description: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.
Project description:Long intergenic noncoding RNAs (lincRNAs) are transcribed from thousands of loci in mammalian genomes and play essential roles in diverse biological processes. Their expression is often restricted to distinct developmental contexts and often exhibits precise cell- and/or tissue-specific localization. Recent studies demonstrated that their sequences are highly enriched for repetitive elements (REs) of retroviral origin that might have contributed to their evolution and function-acquisition through development. However, the molecular mechanism(s) by which they regulate gene networks in a cell type-specific manner is largely unknown. Here, we used single-cell gene expression profiling during nuclear reprogramming and identified three endogenous retrovirus 1 (ERV1)-derived lincRNAs (HPAT2, 3 and 5) that are coordinately expressed along with key factors of the core regulatory pluripotency network (OCT4, NANOG, SOX2, SALL4). Chromatin precipitation and reporter-system based assays revealed that NANOG regulates gene expression of these novel lincRNAs in a methylation-dependent manner. Gain- and loss-of function assays identify HPAT5 as a competing endogenous RNA (ceRNA) that acts to regulate pluripotency via a molecular mechanism in which HPAT5 sequesters specific microRNAs (miRNAs) during nuclear reprogramming or human embryonic stem cell (hESC) differentiation to protect SALL4 from let-7 mediated degradation. These results indicate that primate-specific retroviral-derived lincRNAs may regulate widely-conserved pluripotency pathways in human stem cells via novel mechanisms of competition and sequestration. We used microarrays to study the ceRNA crosstalk on a global level in hESCs lacking the HPAT5 locus.
Project description:Long non-coding RNAs (lncRNAs) play pivotal roles in diseases such as osteoarthritis (OA). However, knowledge of the biological roles of lncRNAs is limited in OA. We aimed to explore the biological function and molecular mechanism of HOTTIP in chondrogenesis and cartilage degradation. We used the human mesenchymal stem cell (MSC) model of chondrogenesis, in parallel with, tissue biopsies from normal and OA cartilage to detect HOTTIP, CCL3, and miR-455-3p expression in vitro. Biological interactions between HOTTIP and miR-455-3p were determined by RNA silencing and overexpression in vitro. We evaluated the effect of HOTTIP on chondrogenesis and degeneration, and its regulation of miR-455-3p via competing endogenous RNA (ceRNA). Our in vitro ceRNA findings were further confirmed within animal models in vivo. Mechanisms of ceRNAs were determined by bioinformatic analysis, a luciferase reporter system, RNA pull-down, and RNA immunoprecipitation (RIP) assays. We found reduced miR-455-3p expression and significantly upregulated lncRNA HOTTIP and CCL3 expression in OA cartilage tissues and chondrocytes. The expression of HOTTIP and CCL3 was increased in chondrocytes treated with interleukin-1β (IL-1β) in vitro. Knockdown of HOTTIP promoted cartilage-specific gene expression and suppressed CCL3. Conversely, HOTTIP overexpression reduced cartilage-specific genes and increased CCL3. Notably, HOTTIP negatively regulated miR-455-3p and increased CCL3 levels in human primary chondrocytes. Mechanistic investigations indicated that HOTTIP functioned as ceRNA for miR-455-3p enhanced CCL3 expression. Taken together, the ceRNA regulatory network of HOTTIP/miR-455-3p/CCL3 plays a critical role in OA pathogenesis and suggests HOTTIP is a potential target in OA therapy.