Regulation Of Dicer Research Articles

USP7 reduces the level of nuclear DICER, impairing DNA damage response and promoting cancer progression.

Endoribonuclease DICER is an RNase III enzyme that mainly processes microRNAs in the cytoplasm but also participates in nuclear functions such as chromatin remodelling, epigenetic modification and DNA damage repair. The expression of nuclear DICER is low in most human cancers, suggesting a tight regulation mechanism that is not well understood. Here, we found that ubiquitin carboxyl-terminal hydrolase 7 (USP7), a deubiquitinase, bounded to DICER and reduced its nuclear protein level by promoting its ubiquitination and degradation through MDM2, a newly identified E3 ubiquitin-protein ligase for DICER. This USP7-MDM2-DICER axis impaired histone γ-H2AX signalling and the recruitment of DNA damage response (DDR) factors, possibly by influencing the processing of small DDR noncoding RNAs. We also showed that this negative regulation of DICER by USP7 via MDM2 was relevant to human tumours using cellular and clinical data. Our findings revealed a new way to understand the role of DICER in malignant tumour development and may offer new insights into the diagnosis, treatment and prognosis of cancers.

RNA and DNA G-quadruplexes bind to human dicer and inhibit its activity

Guanine (G)-rich single-stranded nucleic acids can adopt G-quadruplex structures. Accumulating evidence indicates that G-quadruplexes serve important regulatory roles in fundamental biological processes such as DNA replication, transcription, and translation, while aberrant G-quadruplex formation is linked to genome instability and cancer. Understanding the biological functions played by G-quadruplexes requires detailed knowledge of their protein interactome. Here, we report that both RNA and DNA G-quadruplexes are bound by human Dicer in vitro. Using in vitro binding assays, mutation studies, and computational modeling we demonstrate that G-quadruplexes can interact with the Platform–PAZ–Connector helix cassette of Dicer, the region responsible for anchoring microRNA precursors (pre-miRNAs). Consequently, we show that G-quadruplexes efficiently and stably inhibit the cleavage of pre-miRNA by Dicer. Our data highlight the potential of human Dicer for binding of G-quadruplexes and allow us to propose a G-quadruplex-driven sequestration mechanism of Dicer regulation.

81: Impact of Hypoxia-Mediated Regulation of Dicer on Treatment Outcome in Cervical Cancer

81: Impact of Hypoxia-Mediated Regulation of Dicer on Treatment Outcome in Cervical Cancer

Diagnostic value of plasma expression of microRNAs complementary to Drosha and Dicer in lung cancer patients.

Lung cancer (LC) is diagnosed mostly in advanced, non-operable stage, with poor prognosis. The analysis of microRNAs may be a useful tool for early and non-invasive detection of cancer. Dicer and Drosha are enzymes with an essential role for microRNA biogenesis. The aim of our study was to analyze the expression of miRNA-27a-3p, miRNA-31, miRNA-182, miRNA-195 with the ability to reciprocal regulation of Dicer and Drosha expression in lung cancer patients. The relative expression of microRNAs was detected by qPCR in plasma of 160 LC patients. The U-Mann Whitney test was used to compare the relative expression between particular groups of lung cancer patients and healthy individuals. The diagnostic value of microRNAs examination was analyzed using a receiver operating curve. We demonstrated that the plasma levels of miRNA-27, miRNA-31 and miRNA-182 were significantly higher and miRNA-195 significantly lower in the whole group of LC patients and in patients with early stages of NSCLC, in comparison with healthy donors. ROC analysis showed that four studied microRNAs have a potential diagnostic value for early stages of NSCLC with AUC=0.95 for miRNA-27a (94% sensitivity and 81% specificity, p=0.0001), 0.71 for miRNA-31 (73% sensitivity and 61% specificity, p=0.001) 0.77 for miRNA-182 (70% sensitivity and 79% specificity, p=0.0001) and 0.82 for miRNA-195 (74% sensitivity and 80% specificity, p=0.0001). We have proved that the expression of miRNA-27a-3p, miRNA-31, miRNA-182, and miRNA-195 in patients with LC is different from the expression of these molecules in healthy people. The examination of these microRNAs in plasma could be used in non-invasive lung cancer diagnosis.

SUN-194 Erasing the Methyl Mark: Mechanism of Androgen Action in the Ovary

Androgen actions through androgen receptor (AR) are critical for follicle growth and female fertility. While excess androgen level leads to polycystic ovary syndrome (PCOS), a certain amount of direct androgen action is critical for normal ovarian function. Thus, with respect to androgen actions in the ovary, balance is key. However, how androgens regulate ovarian physiology or its underlying mechanism is still poorly understood. Androgen actions are mediated through ‘nuclear/genomic’ or ‘extra-nuclear/non-genomic’ actions of AR. Recently we reported that androgens through both the extra-nuclear and nuclear pathways inhibit the expression and activity of Ezh2, (a histone methyl-transferase involved in gene repression mark, H3K27me3) to induce different genes that are imperative for ovarian function. Here, we further extended our study to elucidate other histone modifications induced by androgens and its downstream physiological effect in follicular development. In addition to Ezh2, we have found that androgens also regulated the expression of a histone demethylase called Jumonji domain containing protein 3 (JMJD3/KDM6B), that is responsible of removing H3K27me3 mark. Results showed that DHT in GCs increased hypoxia-inducible factor 1 alpha (HIF1α) protein levels through the PI3K/Akt pathway, which in turn induced JMJD3 expression. We found that DHT had not affect HIF1α mRNA but increased HIF1α protein levels. This effect of DHT on HIF1α protein level was blocked by flutamide (AR inhibitor), LY294002 (PI3K inhibitor) as well as cyclohexamide (protein translational inhibitor). Interestingly the 5’ prime end of JMJD3 have HIF1α response elements (HRE) and it is well established that several JMJDs are induced by HIF1α under both normal conditions and hypoxic stress. Our studies showed that DHT treatment induced JMJD3 expression and decreased H3K27me3 levels. Inhibition of AR, PI3K/AKT pathway and siRNA-mediated knockdown of HIF1α attenuated androgen-induced expression of JMJD3. Moreover, ChIP studies showed increased binding of HIF1α on the JMJD3 promoter region with DHT treatment. In our efforts to understand the downstream effects of androgen-induced JMJD3 expression, we found Dicer1 was upregulated upon DHT treatment to mouse granulosa cells. Given the critical role of Dicer in follicular development, ovarian physiology and female fertility, in general, along with the importance of androgens in ovarian physiology, we propose that regulation of Dicer is one of the underlying mechanisms of androgen actions in the ovary. Androgens in a transcription-independent manner, through the PI3K/Akt signaling pathway, enhance HIF1α protein synthesis under normoxic conditions which in turn regulate the expression of Dicer through JMJD3. Altogether, this study provides a mechanistic insight of androgen actions in ovarian function by epigenetic modulation.

MDA-7/IL-24 regulates the miRNA processing enzyme DICER through downregulation of MITF

Melanoma differentiation-associated gene-7/interleukin-24 (mda-7/IL-24) is a multifunctional cytokine displaying broad-spectrum anticancer activity in vitro or in vivo in preclinical animal cancer models and in a phase 1/2 clinical trial in patients with advanced cancers. mda-7/IL-24 targets specific miRNAs, including miR-221 and miR-320, for down-regulation in a cancer-selective manner. We demonstrate that mda-7/IL-24, administered through a replication incompetent type 5 adenovirus (Ad.mda-7) or with His-MDA-7/IL-24 protein, down-regulates DICER, a critical regulator in miRNA processing. This effect is specific for mature miR-221, as it does not affect Pri-miR-221 expression, and the DICER protein, as no changes occur in other miRNA processing cofactors, including DROSHA, PASHA, or Argonaute. DICER is unchanged by Ad.mda-7/IL-24 in normal immortal prostate cells, whereas Ad.mda-7 down-regulates DICER in multiple cancer cells including glioblastoma multiforme and prostate, breast, lung, and liver carcinoma cells. MDA-7/IL-24 protein down-regulates DICER expression through canonical IL-20/IL-22 receptors. Gain- and loss-of-function studies confirm that overexpression of DICER rescues deregulation of miRNAs by mda-7/IL-24, partially rescuing cancer cells from mda-7/IL-24-mediated cell death. Stable overexpression of DICER in cancer cells impedes Ad.mda-7 or His-MDA-7/IL-24 inhibition of cell growth, colony formation, PARP cleavage, and apoptosis. In addition, stable overexpression of DICER renders cancer cells more resistant to Ad.mda-7 inhibition of primary and secondary tumor growth. MDA-7/IL-24-mediated regulation of DICER is reactive oxygen species-dependent and mediated by melanogenesis-associated transcription factor. Our research uncovers a distinct role of mda-7/IL-24 in the regulation of miRNA biogenesis through alteration of the MITF-DICER pathway.

24 - 4-HNE-mediated post-translational modulation of DICER in heart failure

4-hydroxy-2-nonenal (4-HNE) is a major by-product of lipid peroxidation, a process that is exacerbated under oxidative stress conditions. This aldehyde is a very reactive molecule associated with the establishment and progression of many diseases, including cardiovascular diseases. Using mass spectrometry analysis, our group has recently found that 4-HNE directly targets DICER— a critical enzyme for microRNA (miRNA) biology— in failing hearts. Considering that targeted deletion of DICER in the heart leads to dilated cardiomyopathy and heart failure (HF), we hypothesized that 4-HNE adducted DICER could compromise its function and drive cardiac dysfunction. In a post-myocardial infarction-induced HF animal model, we found that DICER activity dropped 46.5% (53,5% ±3,9; n=6) in failing hearts when compared to sham group, followed by a reduction in miRNA levels. Pharmacological activation of aldehyde dehydrogenase 2 (ALDH2), a key mitochondrial enzyme responsible for 4-HNE removal, prevented cardiac 4-HNE protein adduct accumulation and minimized DICER loss of activity (72,15% ±14,6; n=6) in heart failure. Consistent with our in vivo data, H9C2 myoblasts acutely exposed to 50µM 4-HNE showed an increase in 4-HNE-protein adducts followed by a 16,7% reduction (83,3% ±1,2; n=4) in DICER activity. Notably, in vitro experiments using recombinant protein revealed that 4-HNE directly interacts with DICER, and the formation of 4-HNE-DICER adduct causes loss of DICER enzymatic activity in a time- and concentration-dependent manner. Taken together, our findings using animal and cellular models suggest that DICER is impaired under acute and chronic (cardiac dysfunction) aldehyde load. Moreover, a better clearance of cardiac 4-HNE improves both DICER activity and heart failure outcome in rodents. Overall, a better understanding of post-translational DICER regulation and its impact on microRNA profiles will certainly contribute to the discovery/development of improved and novel therapeutic strategies to tackle heart failure.

P1.11-03 MicroRNA with Ability to Reciprocal Regulation of Dicer and Drosha – Plasma Expression Status and Diagnostic Value in Non-Small Cell Lung Cancer

Examination of microRNAs expression in plasma could be useful in screening and in early detection of non-small cell lung cancer (NSCLC). One of the most important enzymes in miRNA biogenesis are Dicer and Drosha. Disrupted expression of miRNA with ability to reciprocal regulation of Dicer and Drosha could participate in cancer development. Plasma expression of miR-27-3p, miR-31, miR-182 and miR-195 were analysed in 138 Polish NSCLC patients (median age 65 years, 83 male and 55 female) and in 45 healthy people (median age 62 years, 28 male and 17 female). 57 (41.3%) NSCLC patient were in I-IIIA stage and 81 (58.7%) patients were in IIIB-IV stage. Relative expression of microRNAs between studied groups was compared using U Mann-Whitney test. For assessment of diagnostic accuracy (test sensitivity and specificity), the receiver operating curves (ROC) with area under curve (AUC) analysis were generated. We demonstrated that plasma levels of miR-27-3p, miR-31 and miR-182 were significantly higher (p<0.000001, p=0.00008, p=0.006 respectively) and miR-195 significantly lower (p=0.000002) in NSCLC patients in comparison with healthy donors. Moreover, patients with early stages (I-IIIA) of NSCLC showed significantly higher expression of miR-27a-3p (p<0.000001), miR-31 (p=0.0003) and miR-182 (p=0.000003) than healthy persons. Expression of miR-195 was significantly lower in patients with early stages (I-IIIA) of NSCLC than in healthy donors (p<0.000001). AUC for miR-27a was 0.95 (94% sensitivity and 81% specificity, p<0.00001), for miR-31 was 0.71 (73% sensitivity and 61% specificity, p=0.001), for miR-182 was 0.77 (70% sensitivity and 79% specificity, p<0.00001) and for miR-195 was 0.82 (74% sensitivity and 80% specificity, p=0.00001). Expression of miR-27a, miR-31, miR-182 and miR-195 could distinguish patients with NSCLC from healthy people. The examination of these microRNAs in plasma could be used in non-invasive lung cancer diagnosis. Deregulation of Dicer and Drosha expression by microRNAs could have oncogenic character.

Hypoxia Causes Downregulation of Dicer in Hepatocellular Carcinoma, Which Is Required for Upregulation of Hypoxia-Inducible Factor 1α and Epithelial-Mesenchymal Transition.

Purpose: A role of Dicer, which converts precursor miRNAs to mature miRNAs, in the tumor-promoting effect of hypoxia is currently emerging in some tumor entities. Its role in hepatocellular carcinoma (HCC) is unknown.Experimental Design: HepG2 and Huh-7 cells were stably transfected with an inducible Dicer expression vector and were exposed to hypoxia/normoxia. HepG2-Dicer xenografts were established in nude mice; hypoxic areas and Dicer were detected in HCC xenografts and HCCs from mice with endogenous hepatocarcinogenesis; and epithelial-mesenchymal transition (EMT) markers were analyzed by immunohistochemistry or by immunoblotting. The correlation between Dicer and carbonic anhydrase 9 (CA9), a marker of hypoxia, was investigated in resected human HCCs.Results: Hypoxia increased EMT markers in vitro and in vivo and led to a downregulation of Dicer in HCC cells. The levels of Dicer were downregulated in hypoxic tumor regions in mice with endogenous hepatocarcinogenesis and in HepG2 xenografts. In human HCCs, the levels of Dicer correlated inversely with those of CA9, indicating that the negative regulation of Dicer by hypoxia also applies to HCC patients. Forced expression of Dicer prevented the hypoxia-induced increase in hypoxia-inducible factor 1α (HIF1α), HIF2α, hypoxia-inducible genes (CA9, glucose transporter 1), EMT markers, and cell migration.Conclusions: We here identify downmodulation of Dicer as novel essential process in hypoxia-induced EMT in HCC and demonstrate that induced expression of Dicer counteracted hypoxia-induced EMT. Thus, targeting hypoxia-induced downmodulation of Dicer is a promising novel strategy to reduce HCC progression. Clin Cancer Res; 23(14); 3896-905. ©2017 AACR.

How short RNAs impact the human ribonuclease Dicer activity: putative regulatory feedback-loops and other RNA-mediated mechanisms controlling microRNA processing.

Ribonuclease Dicer plays a pivotal role in RNA interference pathways by processing long double-stranded RNAs and single-stranded hairpin RNA precursors into small interfering RNAs (siRNAs) and microRNAs (miRNAs), respectively. While details of Dicer regulation by a variety of proteins are being elucidated, less is known about non-protein factors, e.g. RNA molecules, that may influence this enzyme's activity. Therefore, we decided to investigate the question of whether the RNA molecules can function not only as Dicer substrates but also as its regulators. Our previous in vitro studies indicated that the activity of human Dicer can be influenced by short RNA molecules that either bind to Dicer or interact with its substrates, or both. Those studies were carried out with commercial Dicer preparations. Nevertheless, such preparations are usually not homogeneous enough to carry out more detailed RNA-binding studies. Therefore, we have established our own system for the production of human Dicer in insect cells. In this manuscript, we characterize the RNA-binding and RNA-cleavage properties of the obtained preparation. We demonstrate that Dicer can efficiently bind single-stranded RNAs that are longer than ~20-nucleotides. Consequently, we revisit possible scenarios of Dicer regulation by single-stranded RNA species ranging from ~10- to ~60-nucleotides, in the context of their binding to this enzyme. Finally, we show that siRNA/miRNA-sized RNAs may affect miRNA production either by binding to Dicer or by participating in regulatory feedback-loops. Altogether, our studies suggest a broad regulatory role of short RNAs in Dicer functioning.

The epigenetic regulation of Dicer and microRNA biogenesis by Panobinostat

ABSTRACTmicroRNAs (miRs) are small noncoding RNAs that regulate/fine tune many cellular protein networks by targeting mRNAs for either degradation or translational inhibition. Dicer, a type III endoribonuclease, is a critical component in miR biogenesis and is required for mature microRNA production. Abnormal Dicer expression occurs in numerous cancer types and correlates with poor patient prognosis. Recent reports have demonstrated that epigenetic agents, including histone deacetylase inhibitors (HDACi), may regulate Dicer and miR expression. HDACi are a class of epigenetic agents used to treat cancer, viral infections, and inflammatory disorders. However, little is known regarding the epigenetic regulation of miR biogenesis and function. We therefore investigated whether clinically successful HDACi modulated Dicer expression and found that Panobinostat, a clinically approved HDACi, enhanced Dicer expression via posttranscriptional mechanisms. Studies using proteasome inhibitors suggested that Panobinostat regulated the proteasomal degradation of Dicer. Further studies demonstrated that Panobinostat, despite increasing Dicer protein expression, decreased Dicer activity. This suggests that Dicer protein levels do not necessarily correlate with Dicer activity and mature miR levels. Taken together, we present evidence here that Panobinostat posttranscriptionally regulates Dicer/miR biogenesis and suggest Dicer as a potential therapeutic target in cancer.

MicroRNA-18a Promotes Cell Migration and Invasion Through Inhibiting Dicer l Expression in Hepatocellular Carcinoma In Vitro.

Objective To investigate the effects of microRNA-18a (miR-18a) on migration and invasion of hepatocellular carcinoma (HCC) cells, and its possible mechanism associated with Dicer l.Methods HepG2 and HepG2.2.15 cells were transfected with miR-18a inhibitor using Lipofectamine. Cell invasion was evaluated by transwell invasion assay, and cell migration was detected by transwell migration and wound-healing assays. Moreover, luciferase reporter assay was used to identify whether Dicer expression was regulated by miR-18a. Real-time RT-PCR and western blot were performed to analyze Dicer 1 expression. In addition, a functional restoration assay was performed to investigate whether miR-18a promotes HCC cell migration and invasion by directly targeting Dicer 1.Results miR-18a inhibitor can suppress the migration and invasion of HCC cells. Furthermore, suppression of Dicer l expression by small interfering RNA essentially abolished the inhibition of cell migration and invasion induced by miR-18a inhibitor, restorating these activities to levels similar to the parental HCC cells. Interestingly, suppression of miR-18a in HCC cells resulted in enhanced expression of Dicer l. In addition, the results of a luciferase assay demonstrated targeted regulation of Dicer l by miR-18a.Conclusion Our findings suggest that miR-18a promotes migration and invasion of HCC cells by inhibiting Dicer l expression.

TWEAK Negatively Regulates Human Dicer.

The ribonuclease Dicer plays a central role in the microRNA pathway by processing microRNA precursors (pre-microRNAs) into microRNAs, a class of 19- to 24-nucleotide non-coding RNAs that regulate expression of ≈60% of the genes in humans. To gain further insights into the function and regulation of Dicer in human cells, we performed a yeast two-hybrid (Y2HB) screen using human Dicer double-stranded RNA-binding domain (dsRBD) as bait. This approach identified tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) as a Dicer-interacting protein candidate. Confocal immunofluorescence microscopy revealed the colocalization of Dicer and TWEAK proteins at the perinuclear region of HeLa cells. The Dicer-TWEAK protein interaction was confirmed by coimmunoprecipitation and found not likely to be mediated by RNA. TWEAK dose-dependently reduced pre-microRNA conversion into mature microRNA in Dicer activity assays using extracts of transfected human HEK 293 cells. TWEAK expression also impaired microRNA-guided RNA silencing of a reporter gene induced by a pre-microRNA. These findings suggest a role for TWEAK—a pro-inflammatory cytokine—in regulating Dicer function and microRNA biogenesis, and its possible involvement in regulating gene expression during inflammatory processes and diseases.

Dicer and microRNA expression in multiple sclerosis and response to interferon therapy

Dysregulation of microRNA expression has been shown in multiple sclerosis (MS); however, the mechanisms underlying these changes, their response to therapy and the impact of microRNA changes in MS are not completely understood. Dicer mediates the cleavage of precursor microRNAs to mature microRNAs and is dysregulated in multiple pathologies. Having shown that interferons regulate Dicer in vitro, we hypothesized that MS patient IFNβ1a treatment could potentially alter Dicer expression. Dicer mRNA and protein levels, as well as microRNA expression, were determined in MS patient and healthy control PBL. Acute responses to IFNβ1a were assessed in 50 patients. We found that Dicer protein but not mRNA levels decreases in MS patients while both are selectively induced in patients responding well to IFNβ1a. Potential microRNA biomarkers for relapsing remitting multiple sclerosis (RRMS), secondary progressive multiple sclerosis (SPMS) and IFNβ1a response are described. Contrasts in Dicer and microRNA expression levels between patient populations may offer insight into mechanisms underlying disease courses and responses to IFNβ1a therapy. This work identifies Dicer regulation as both a potential mediator of MS pathology and a therapeutic target.

Abstract 199: Functional mechanism of hypoxia-inducible factor 1 alpha-mediated Dicer down-regulation

Abstract MicroRNAs (miRNAs) are generated by a multiple steps process that post-transcriptionally regulate the expression of target genes. Dysregulation of miRNAs is linked to human diseases including the development of human cancer. Abrogation of cellular global miRNAs maturation has been proposed to promote tumorigenesis and cancer metastasis. Hypoxia stress is the major cause of dysregulation of miRNAs and promotes tumor angiogenesis, metastasis and tumorigenesis which is a pivotal factor to switch on the cellular oncogenic features during tumor progression. Although hypoxia stress regulates expression of a subset of miRNAs, the upstream regulators controlling miRNAs regulation under hypoxia remain unclear. This study demonstrates the molecular mechanism of post-translational regulation of Dicer under hypoxia. Our results show that knockdown of hypoxia inducible factor 1 alpha (HIF-1α) up-regulates Dicer expression in colorectal cancer (CRC) cells. Overexpression of HIF-1α enhances ubiquitination of Dicer and subsequently promotes it recognition by autophagic receptor for autophagy-lysosomal degradation. We also find that HIF-1α enhances cancer cell migration by regulating Dicer-regulated miRNAs. In conclusion, we demonstrated that HIF-1α down-regulated Dicer and abolishes miRNA biogenesis to enhance cancer cell migration. This study may provide a potential therapeutic direction that targets the dysregulated miRNAs in tumor hypoxia for patients with poor prognosis and metastatic CRC. Citation Format: Hui-Huang Lai, Yu-Jhen Lyu, Jie-Ning Li, Jen-Liang Su, Pai-Sheng Chen. Functional mechanism of hypoxia-inducible factor 1 alpha-mediated Dicer down-regulation. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 199. doi:10.1158/1538-7445.AM2015-199

The expression and clinical significance of microRNA-107 in bladder transitional cell carcinoma

Objective To detect the expression level of microRNA(miR)- 107 in the different clinical stages of bladder transitional cell carcinoma(BTCC), and explore the relationship between miR- 107 pathway and clinicopathological features of BTCC. Methods Fifty- six BTCC specimens surgically resected were selected.For each specimen, the cancerous tissue and its remote normal mucosa were analyzed and compared.The expression of miR- 107, let- 7, Dicer, Ras/high mobility group A2(HMGA2), and zinc-finger E-box binding homeobox 1(ZEB1)/zinc-finger E-box binding homeobox 2(ZEB2)in the resected cancer tissues was detected by using real- time quantitative polymerase chain reaction(Real- time PCR), Western blotting and immunohistochemistry, and their correlation with clinicopathological features was analyzed. Results (1) The expression rate of miR-107 was significantly higher in BTCC tissues than in normal tissues(14.983±6.215 vs.9.124±5.595), and that in deeply infiltrating group was significantly higher than that in superficially infiltrating group (15.183±6.035 vs.11.728±5.472, and 14.663±5.215 vs.10.983±5.674,P 0.05).Ras/ HMGA2, let- 7 downstream regulatory factors, were significantly higher in BTCC than in normal tissues(89.3% vs.23.2%, and 80.3% vs.28.6%,P< 0.05). The expression of let- 7, and Dicer in BTCC tissues was significantly lower than in normal bladder epithelium (P< 0.05);(2) miR- 107 expression was inversely correlated to let- 7 and Dicer. Conclusion The miR- 107 was related with the clinical stages of BTCC through the regulation of Dicer and let- 7 pathways, which mediates the occurrence and development of bladder cancer. Key words: Micro RNA- 107; Dicer; Bladder transitional cell carcinoma; Epithelialmesenchymal transition

Hypoxia promotes stem cell phenotypes and poor prognosis through epigenetic regulation of DICER.

MicroRNAs are small regulatory RNAs that post-transcriptionally control gene expression. Reduced expression of DICER, the enzyme involved in microRNA processing, is frequently observed in cancer and is associated with poor clinical outcome in various malignancies. Yet the underlying mechanisms are not well understood. Here, we identify tumor hypoxia as a regulator of DICER expression in large cohorts of breast cancer patients. We show that DICER expression is suppressed by hypoxia through an epigenetic mechanism that involves inhibition of oxygen-dependent H3K27me3 demethylases KDM6A/B and results in silencing of the DICER promoter. Subsequently, reduced miRNA processing leads to derepression of the miR-200 target ZEB1, stimulates the epithelial to mesenchymal transition and ultimately results in the acquisition of stem cell phenotypes in human mammary epithelial cells. Our study uncovers a previously unknown relationship between oxygen-sensitive epigenetic regulators, miRNA biogenesis and tumor stem cell phenotypes that may underlie poor outcome in breast cancer.

Dicer mediating the expression of miR-143 and miR-155 regulates hexokinase II associated cellular response to hypoxia.

Lung alveolar epithelial cells are exposed to hypoxia under a variety of physiological and pathological conditions. It has been shown recently that miR-143, which can directly target the key glycolytic enzyme hexokinase II (HK2), may be regulated by miR-155. We investigated whether microRNAs contribute to the cellular glycolysis in response to hypoxia. Using the A549 cells, we found that the expression of Dicer is decreased under hypoxia. When Dicer was knocked down with small-interfering RNA (siRNA), pre-miR143 was increased and mature miR-143 was decreased as that in hypoxia, indicating that reduction of Dicer is responsible for the change of miR-143 under hypoxia. Interestingly, both hypoxia and knockdown of Dicer resulted in miR-155 and pre-miR-155 expression increases. We also examined the expression of HK2 and glucose metabolism in the cells. Both HK2 mRNA and protein were increased under hypoxia, which is accompanied by an increase of glucose uptake and production of lactate. The same alterations were found with siRNA Dicer knockdown. Moreover, transfection with anti-miR-143 also led to a HK2 production and an increase of glucose uptake and lactate production, whereas anti-miR-155 had opposite effects. The miR-143 and anti-miR-155 transfection resulted in a significant cell apoptosis. The expression of Dicer was decreased with HK2 accumulating in mouse lung tissues under hypoxia identified by immunohistochemistry. The changes of miR-143 and miR-155 were similar to those in A549 cells. Our data demonstrate that Dicer regulation of miRNAs promotes HK2 activation and glycolysis, which might protect the cell from hypoxic damage and enter into an adaptive process.

The Hippo Pathway Effectors TAZ/YAP Regulate Dicer Expression and MicroRNA Biogenesis through Let-7

MicroRNAs (miRNAs) are genome-encoded small double-stranded RNAs that have emerged as key regulators of gene expression and are implicated in most aspects of human development and disease. Canonical miRNA biogenesis involves processing of ∼70-nucleotide pre-miRNA hairpins by Dicer to generate mature ∼22-nucleotide miRNAs, which target complementary RNA sequences. Despite the importance of miRNA biogenesis, signaling mechanisms controlling this process are poorly defined. Here we demonstrate that the post-transcriptional regulation of Dicer is controlled by the cell density-mediated localization of the Hippo pathway effectors TAZ (transcriptional co-activator with PDZ-binding motif) and YAP (Yes-associated protein) (TAZ/YAP). We show that nuclear TAZ/YAP, which are abundant at low cell density, are required for efficient pre-miRNA processing. Knockdown of TAZ/YAP in low density cells, or density-mediated sequestration of TAZ/YAP into the cytoplasm, results in the defective processing of pre-miRNAs. Strikingly, one exception is Let-7, which accumulates upon loss of nuclear TAZ/YAP, leading to Let-7-dependent reduction in Dicer levels. Accordingly, inhibition of Let-7 rescues the miRNA biogenesis defects observed following TAZ/YAP knockdown. Thus, density-regulated TAZ/YAP localization defines a critical and previously unrecognized mechanism by which cells relay cell contact-induced cues to control miRNA biogenesis.

Valproic Acid Causes Proteasomal Degradation of DICER and Influences miRNA Expression

Valproic acid (VPA) is a commonly used drug to treat epilepsy and bipolar disorders. Known properties of VPA are inhibitions of histone deacetylases and activation of extracellular signal regulated kinases (ERK), which cannot fully explain VPA’s clinical features. We found that VPA induces the proteasomal degradation of DICER, a key protein in the generation of micro RNAs. Unexpectedly, the concentration of several micro RNAs increases after VPA treatment, which is caused by the upregulation of their hosting genes prior to DICER degradation. The data suggest that a loss of DICER protein and changes in micro RNA concentration contributes to the clinical properties of VPA. VPA can be used experimentally to down regulate DICER protein levels, which likely reflects a natural regulation of DICER.