Project description:Circular RNAs (circRNAs), a noncoding RNA class originating from alternative splicing, are highly abundant in neural tissues and were shown to regulate gene expression e.g. by interacting with microRNAs and RNA-binding proteins. Neuroblastoma is an embryonal neoplasia, which arises from undifferentiated neural crest cells. Here, we aimed to explore, whether circRNAs influence the pathogenesis of high-risk neuroblastoma. We performed whole-transcriptome sequencing of 104 primary neuroblastoma samples of all risk-groups and identified 5,203 unique circRNAs involving 2,302 genes. Candidate circRNA expression did not correlate with host gene expression, indicating independent regulatory mechanisms. circRNAs were significantly downregulated in the MYCN-amplified high-risk tumors. These findings were independently reproduced in a tetracycline-inducible MYCN-overexpression system based on a non MYCN-amplified neuroblastoma cell line, suggesting that MYCN drives this global circRNA repression. We identified the RNA helicase DHX9 as a mediator of this global suppressive effect of MYCN on circRNAs. Comparing our RNA sequencing data with other cancers and controls revealed a circRNA subset specifically upregulated in neuroblastoma that included a circRNA derived from the ARID1A tumor suppressor gene. Specific circARID1A knockdown resulted in reduced proliferation, cell numbers and viability, prompted apoptosis and induced a differentiated phenotype. Neither knockdown, nor overexpression of circARID1A influenced ARID1A mRNA and protein levels significantly. To dissect the potential mode of function, we performed a pulldown assay with subsequent mass spectrometry. We identified the RNA-binding protein KHSRP as an interaction partner that participates in the mechanism of action of circARID1A. In summary, this study highlights an important role of circRNAs in neuroblastoma biology and may establish this RNA class as a future therapeutic target and biomarker.
Project description:Arraystar Human circRNA Microarray is designed for the global profiling of human circRNAs. In this study, we applied a circRNA microarray to screen the potential biomarker for HCC. 20 samples extracted from plasma samples including HCC group before operation, and after operation, CH group and control group. Each group contained five samples.
Project description:Circular RNAs (circRNAs) are covalently closed non-coding RNAs lacking the 5’ cap and the poly-A tail. Nevertheless, it has been demonstrated that certain circRNAs can undergo active translation. Therefore, aberrantly expressed circRNAs in human cancers could be an unexplored source of tumor-specific antigens, potentially mediating anti-tumor T cell responses. This study presents an immunopeptidomics workflow with a specific focus on generating a circRNA-specific protein fasta reference. The main goal of this workflow is to streamline the process of identifying and validating human leukocyte antigen (HLA) bound peptides potentially originating from circRNAs. We increased the analytical stringency of our workflow by retaining peptides identified independently by two mass spectrometry search engines and/or by applying a group-specific FDR for canonical-derived and circRNA-derived peptides. A subset of circRNA-derived peptides specifically encoded by the region spanning the back-splice junction (BSJ) were validated with targeted MS, and with direct Sanger sequencing of the respective source transcripts. Our workflow identified 54 unique BSJ-spanning circRNA-derived peptides in the immunopeptidome of melanoma and lung cancer samples. Our novel approach enlarges the catalog of source proteins that can be explored for immunotherapy.
Project description:Circular RNA (circRNA) has recently gained attention for its emerging biological activities, relevance to disease, and potential as biomarkers. Furthermore, the growing prominence of RNA vaccines has brought circRNAs into the spotlight as a promising alternative modality due to their enhanced stability compared to linear RNA. Nevertheless, sequencing circRNAs has presented challenges. In this context, we introduce a novel circRNA sequencing method called Induro-RT mediated circRNA-sequencing (IMCR-seq), which relies on a group II intron reverse transcriptase with robust rolling circle reverse transcription activity. The IMCR-seq protocol eliminates the need for conventional circRNA enrichment methods such as rRNA depletion and RNaseR digestion yet achieved the highest circRNA enrichment and detected 6-1000 times more circRNAs for the benchmarked human samples compared to other methods. IMCR-seq is applicable to any organism, capable of detecting circRNAs of more than 7,000 nucleotides, and is effective using as little as 10 ng of total RNA. These enhancements render IMCR-seq suitable for clinical samples, including disease tissues and liquid biopsies. To demonstrate IMCR-seq's clinical relevance, we applied it to lung tumor tissue and plasma samples from a healthy individual and a lung cancer patient and detected cancer-specific circRNAs as potential biomarkers. In summary, IMCR-seq presents an efficient and versatile circRNA sequencing method with high potential for research and clinical applications.
Project description:We determined circRNA abundance in fly Heads and S2 cells by generating and analyzing high-throughput RNA-sequencing libraries prepared from rRNA-depleted RNA. In order to determine whether the observed sequencing reads are due to bona fide circRNAs, we pre-treated the RNA with RNAse-R before the rRNA-depletion procedure. Indeed, most of the identified circRNAs were more enriched in comparison to the canonical mRNA isoforms following the RNAse-R treatment. We compare circRNA levels in wt (Canton S) flies with flies carrying the C4 ("slow polymerase") mutation. 4 samples of Drosophila Canton S and 4 samples of flies carrying the C4 ("slow polymerase") mutation. For each sample, one library was prepared from RNA after RNaseR treatment and the second from RNA with without treatment (mock). RNA library from one Canton Sample was used for stranded libray preprepation.