RNF183 Promotes Colon Cancer Cell Stemness through Fatty Acid Oxidation.

Colon cancer (COAD) is a prevalent gastrointestinal tumor, composed of a few cancer stem cells (CSCs). High expression of RNF183 drives colorectal cancer metastasis, but its role in COAD cell stemness is still unclear. Bioinformatics analyzed expression and enriched pathway of RNF183 in COAD tissue. IHC analyzed RNF183 protein expression in tumor tissue. CD133 + CD44+ CSCs were sorted by flow cytometry, and RNF183 expression in COAD cells or CSCs was detected by qPCR, western blot and immunofluorescence. CCK-8 assay assessed cell viability, and sphere formation assay tested cell sphere-forming ability. Western blot measured protein expression of stem cell markers. qPCR assayed expression of fatty acid oxidation genes. The ability of fatty acid oxidation was analyzed by detecting fatty acid metabolism. RNF183 was highly expressed in COAD and CD133 + CD44+ CSCs, and was enriched in fatty acid metabolism pathway. RNF183 expression was positively correlated with enzymes involved in fatty acid oxidation. RNF183 could promote COAD stemness and fatty acid oxidation. Rescue experiments showed that Orlistat (a fatty acid oxidation inhibitor) reversed stimulative impact of RNF183 overexpression on COAD stemness. RNF183 promoted COAD stemness by affecting fatty acid oxidation, which may be a new therapeutic target for inhibiting COAD development.

A new method to synthesize multiple gRNA libraries and functional mapping of mammalian H3K4me3 regions.

Genetic screening based on the clustered regularly interspaced palindromic repeat (CRISPR) system has been indicated to be a powerful tool for identifying regulatory genes or cis-elements. However, when applying CRISPR screens to pinpoint functional elements at particular loci, a large number of guide RNA (gRNA) spacers may be required to achieve saturated coverage. Here, we present a controlled template-dependent elongation (CTDE) method relying on reversible terminators to synthesize gRNA libraries with genomic regions of interest. By applying this approach to H3K4me3 chromatin immunoprecipitation (ChIP)-derived DNA of mammalian cells, mega-sized gRNA libraries were synthesized in a tissue-specific manner, with which we conducted screening experiments to annotate essential sites for cell proliferation. Additionally, we confirmed that an essential site within the intron of LINC00339 regulates its own mRNA and that LINC00339 is a novel regulator of the cell cycle that maintains HepG2 proliferation. The CTDE method has the potential to be automated with high efficiency at low cost, and will be widely used to identify functional elements in mammalian genomes.

Construction and Validation of Novel Diagnostic and Prognostic DNA Methylation Signatures for Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is one of the most prevalent life-threatening human cancers and the leading cause of cancer-related mortality, with increased global incidence within the last decade. Identification of effective diagnostic and prognostic biomarkers would enable reliable risk stratification and efficient screening of high-risk patients, thereby facilitating clinical decision-making. Herein, we performed a comprehensive, robust DNA methylation analysis based on genome-wide DNA methylation profiling. We constructed a diagnostic signature with five DNA methylation markers, which precisely distinguished HCC patients from normal controls. Cox regression and LASSO analysis were applied to construct a prognostic signature with four DNA methylation markers. A one-to-one correlation analysis was carried out between genes of the whole genome and our prognostic signature. Exploration of the biological function and the role of the underlying significantly correlated genes was conducted. A mixed dataset of 463 HCC patients and 253 normal controls, derived from six independent datasets, was used to valid the diagnostic signature. Results showed a specificity of 96.84% and sensitivity of 96.77%. Class scores for the diagnostic signature were significantly different between normal controls, individuals with liver diseases, and HCC patients. The present signature has the potential to serve as a biomarker to monitor health in normal controls. Additionally, HCC patients were successfully separated into low-risk and high-risk groups by the prognostic signature, with a better prognosis for patients in the low-risk group. Kaplan-Meier and ROC analysis confirmed that the prognostic signature performed well. We found eight of the top ten genes to positively correlate with risk scores of the prognostic signature, and to be involved in cell cycle regulation. This eight-gene panel also served as a prognostic signature. The robust evidence presented in this study therefore demonstrates the effectiveness of the prognostic signature. In summary, we constructed diagnostic and prognostic signatures, which have potential for use in diagnosis, surveillance, and prognostic prediction for HCC patients. Eight genes that were significantly and positively correlated with the prognostic signature were strongly associated with cell cycle processes. Therefore, the prognostic signature can be used as a guide by which to measure responsiveness to cell-cycle-targeting agents.

Holo-Seq: single-cell sequencing of holo-transcriptome.

Current single-cell RNA-seq approaches are hindered by preamplification bias, loss of strand of origin information, and the inability to observe small-RNA and mRNA dual transcriptomes. Here, we introduce a single-cell holo-transcriptome sequencing (Holo-Seq) that overcomes all three hurdles. Holo-Seq has the same quantitative accuracy and uniform coverage with a complete strand of origin information as bulk RNA-seq. Most importantly, Holo-Seq can simultaneously observe small RNAs and mRNAs in a single cell. Furthermore, we acquire small RNA and mRNA dual transcriptomes of 32 human hepatocellular carcinoma single cells, which display the genome-wide super-enhancer activity and hepatic neoplasm kinetics of these cells.

Hepatic loss of Lissencephaly 1 (Lis1) induces fatty liver and accelerates liver tumorigenesis in mice.

The liver is a major organ in lipid metabolism, and its malfunction leads to various diseases. Nonalcoholic fatty liver disease, the most common chronic liver disorder in developed countries, is characterized by the abnormal retention of excess lipid within hepatocytes and predisposes individuals to liver cancer. We previously reported that the levels of Lissencephaly 1 (LIS1, also known as PAFAH1B1) are down-regulated in human hepatocellular carcinoma. Following up on this observation, we found that genetic deletion of Lis1 in the mouse liver increases lipid accumulation and inflammation in this organ. Further analysis revealed that loss of Lis1 triggers endoplasmic reticulum (ER) stress and reduces triglyceride secretion. Attenuation of ER stress by addition of tauroursodeoxycholic acid (TUDCA) diminished lipid accumulation in the Lis1-deficient hepatocytes. Moreover, the Golgi stacks were disorganized in Lis1-deficient liver cells. Of note, the Lis1 liver-knockout mice exhibited increased hepatocyte ploidy and accelerated development of liver cancer after exposure to the liver carcinogen diethylnitrosamine (DEN). Taken together, these findings suggest that reduced Lis1 levels can spur the development of liver diseases from steatosis to liver cancer and provide a useful model for delineating the molecular pathways that lead to these diseases.

Breast cancer metastasis suppressor OTUD1 deubiquitinates SMAD7.

Metastasis is the main cause of death in cancer patients. TGF-ß is pro-metastatic for malignant cancer cells. Here we report a loss-of-function screen in mice with metastasis as readout and identify OTUD1 as a metastasis-repressing factor. OTUD1-silenced cancer cells show mesenchymal and stem-cell-like characteristics. Further investigation reveals that OTUD1 directly deubiquitinates the TGF-ß pathway inhibitor SMAD7 and prevents its degradation. Moreover, OTUD1 cleaves Lysine 33-linked poly-ubiquitin chains of SMAD7 Lysine 220, which exposes the SMAD7 PY motif, enabling SMURF2 binding and subsequent TßRI turnover at the cell surface. Importantly, OTUD1 is lost in multiple types of human cancers and loss of OTUD1 increases metastasis in intracardial xenograft and orthotopic transplantation models, and correlates with poor prognosis among breast cancer patients. High levels of OTUD1 inhibit cancer stemness and shut off metastasis. Thus, OTUD1 represses breast cancer metastasis by mitigating TGF-ß-induced pro-oncogenic responses via deubiquitination of SMAD7.

Mitochondrial dynamics controls anti-tumour innate immunity by regulating CHIP-IRF1 axis stability.

Macrophages, dendritic cells and other innate immune cells are involved in inflammation and host defense against infection. Metabolic shifts in mitochondrial dynamics may be involved in Toll-like receptor agonist-mediated inflammatory responses and immune cell polarization. However, whether the mitochondrial morphology in myeloid immune cells affects anti-tumor immunity is unclear. Here we show that FAM73b, a mitochondrial outer membrane protein, has a pivotal function in Toll-like receptor-regulated mitochondrial morphology switching from fusion to fission. Switching to mitochondrial fission via ablation of Fam73b (also known as Miga2) promotes IL-12 production. In tumor-associated macrophages, this switch results in T-cell activation and enhances anti-tumor immunity. We also show that the mitochondrial morphology affects Parkin expression and its recruitment to mitochondria. Parkin controls the stability of the downstream CHIP-IRF1 axis through proteolysis. Our findings identify mechanisms associated with mitochondrial dynamics that control anti-tumor immune responses and that are potential targets for cancer immunotherapy.

YAP antagonizes innate antiviral immunity and is targeted for lysosomal degradation through IKKɛ-mediated phosphorylation.

The transcription regulator YAP controls organ size by regulating cell growth, proliferation and apoptosis. However, whether YAP has a role in innate antiviral immunity is largely unknown. Here we found that YAP negatively regulated an antiviral immune response. YAP deficiency resulted in enhanced innate immunity, a diminished viral load, and morbidity in vivo. YAP blocked dimerization of the transcription factor IRF3 and impeded translocation of IRF3 to the nucleus after viral infection. Notably, virus-activated kinase IKKɛ phosphorylated YAP at Ser403 and thereby triggered degradation of YAP in lysosomes and, consequently, relief of YAP-mediated inhibition of the cellular antiviral response. These findings not only establish YAP as a modulator of the activation of IRF3 but also identify a previously unknown regulatory mechanism independent of the kinases Hippo and LATS via which YAP is controlled by the innate immune pathway.

FAF1 phosphorylation by AKT accumulates TGF-ß type II receptor and drives breast cancer metastasis.

TGF-ß is pro-metastatic for the late-stage breast cancer cells. Despite recent progress, the regulation of TGF-ß type II receptor remains uncertain. Here we report that FAF1 destabilizes TßRII on the cell surface by recruiting the VCP/E3 ligase complex, thereby limiting excessive TGF-ß response. Importantly, activated AKT directly phosphorylates FAF1 at Ser 582, which disrupts the FAF1-VCP complex and reduces FAF1 at the plasma membrane. The latter results in an increase in TßRII at the cell surface that promotes both TGF-ß-induced SMAD and non-SMAD signalling. We uncover a metastasis suppressing role for FAF1 through analyses of FAF1-knockout animals, various in vitro and in vivo models of epithelial-to-mesenchymal transition and metastasis, an MMTV-PyMT transgenic mouse model of mammary tumour progression and clinical breast cancer samples. These findings describe a previously uncharacterized mechanism by which TßRII is tightly controlled. Together, we reveal how SMAD and AKT pathways interact to confer pro-oncogenic responses to TGF-ß.

Low-Cell-Number Epigenome Profiling Aids the Study of Lens Aging and Hematopoiesis.

Understanding how chromatin modification regulates development and disease can be limited by available material. Despite recent progress, balancing high-quality and reliable mapping using chromatin-immunoprecipitation-based deep sequencing (ChIP-seq) remains a challenge. We report two techniques, recovery via protection (RP)-ChIP-seq and favored amplification RP-ChIP-seq (FARP-ChIP-seq), that provide reproducible mapping in as few as 500 cells. RP-ChIP-seq allows detection of age-associated epigenetic changes in a single mouse lens, whereas FARP-ChIP-seq accurately maps histone H3 lysine 4 trimethylation (H3K4me3) and H3K27me3 in long-term hematopoietic stem cells (LT-HSCs), short-term HSCs (ST-HSCs), and multi-potent progenitors (MPPs) from one mouse. These datasets not only highlight genes that may be involved in lens aging but also indicate a lack of H3K4me3/H3K27me3 bivalency on hematopoietic genes in HSCs.

Regulation of pluripotency and self- renewal of ESCs through epigenetic-threshold modulation and mRNA pruning.

Embryonic stem cell (ESC) pluripotency requires bivalent epigenetic modifications of key developmental genes regulated by various transcription factors and chromatin-modifying enzymes. How these factors coordinate with one another to maintain the bivalent chromatin state so that ESCs can undergo rapid self-renewal while retaining pluripotency is poorly understood. We report that Utf1, a target of Oct4 and Sox2, is a bivalent chromatin component that buffers poised states of bivalent genes. By limiting PRC2 loading and histone 3 lysine-27 trimethylation, Utf1 sets proper activation thresholds for bivalent genes. It also promotes nuclear tagging of messenger RNAs (mRNAs) transcribed from insufficiently silenced bivalent genes for cytoplasmic degradation through mRNA decapping. These opposing functions of Utf1 promote coordinated differentiation. The mRNA degradation function also ensures rapid cell proliferation by blocking the Myc-Arf feedback control. Thus, Utf1 couples the core pluripotency factors with Myc and PRC2 networks to promote the pluripotency and proliferation of ESCs.

Physiological oxygen level is critical for modeling neuronal metabolism in vitro.

In vitro models are important tools for studying the mechanisms that govern neuronal responses to injury. Most neuronal culture methods employ nonphysiological conditions with regard to metabolic parameters. Standard neuronal cell culture is performed at ambient (21%) oxygen levels, whereas actual tissue oxygen levels in the mammalian brain range from 1% to 5%. In this study, we examined the consequences of oxygen level on the viability and metabolism of primary cultures of cortical neurons. Our results indicate that physiological oxygen level (5% O(2)) has a beneficial effect on cortical neuronal survival and mitochondrial function in vitro. Moreover, oxygen level affects metabolic fluxes: glucose uptake and glycolysis was enhanced at physiological oxygen level, whereas glucose oxidation and fatty acid oxidation were reduced. Adenosine monophosphate-activated protein kinase (AMPK) was more activated in 5% O(2) and appears to play a role in these metabolic effects. Inhibiting AMPK activity with compound C decreased glucose uptake, intracellular ATP level, and viability in neurons cultured in 5% O(2). These data indicate that oxygen level is an important parameter to consider when modeling neuronal responses to stress in vitro.

The Notch signaling pathway controls the size of the ocular lens by directly suppressing p57Kip2 expression.

The size of an organ must be tightly controlled so that it fits within an organism. The mammalian lens is a relatively simple organ composed of terminally differentiated, amitotic lens fiber cells capped on the anterior surface by a layer of immature, mitotic epithelial cells. The proliferation of lens epithelial cells fuels the growth of the lens, thus controling the size of the lens. We report that the Notch signaling pathway defines the boundary between proliferation and differentiation in the developing lens. The loss of Notch signaling results in the loss of epithelial cells to differentiation and a much smaller lens. We found that the Notch effector Herp2 is expressed in lens epithelium and directly suppresses p57Kip2 expression, providing a molecular link between Notch signaling and the cell cycle control machinery during lens development.