Circular RNAs (circRNAs) are a large class of transcripts in the mammalian genome. Although the translation of circRNAs was reported, additional coding circRNAs and the functions of their translated ...products remain elusive. Here, we demonstrate that an endogenous circRNA generated from a long noncoding RNA encodes regulatory peptides. Through ribosome nascent-chain complex-bound RNA sequencing (RNC-seq), we discover several peptides potentially encoded by circRNAs. We identify an 87-amino-acid peptide encoded by the circular form of the long intergenic non-protein-coding RNA p53-induced transcript (LINC-PINT) that suppresses glioblastoma cell proliferation in vitro and in vivo. This peptide directly interacts with polymerase associated factor complex (PAF1c) and inhibits the transcriptional elongation of multiple oncogenes. The expression of this peptide and its corresponding circRNA are decreased in glioblastoma compared with the levels in normal tissues. Our results establish the existence of peptides encoded by circRNAs and demonstrate their potential functions in glioblastoma tumorigenesis.
Circular RNAs (circRNAs) are recognized as functional non-coding transcripts in eukaryotic cells. Recent evidence has indicated that even though circRNAs are generally expressed at low levels, they ...may be involved in many physiological or pathological processes, such as gene regulation, tissue development and carcinogenesis. Although the 'microRNA sponge' function is well characterized, most circRNAs do not contain perfect trapping sites for microRNAs, which suggests the possibility that circRNAs have functions that have not yet been defined. In this study, we show that a circRNA containing an open reading frame (ORF) driven by the internal ribosome entry site (IRES) can translate a functional protein. The circular form of the SNF2 histone linker PHD RING helicase (SHPRH) gene encodes a novel protein that we termed SHPRH-146aa. Circular SHPRH (circ-SHPRH) uses overlapping genetic codes to generate a 'UGA' stop codon, which results in the translation of the 17 kDa SHPRH-146aa. Both circ-SHPRH and SHPRH-146aa are abundantly expressed in normal human brains and are down-regulated in glioblastoma. The overexpression of SHPRH-146aa in U251 and U373 glioblastoma cells reduces their malignant behavior and tumorigenicity in vitro and in vivo. Mechanistically, SHPRH-146aa protects full-length SHPRH from degradation by the ubiquitin proteasome. Stabilized SHPRH sequentially ubiquitinates proliferating cell nuclear antigen (PCNA) as an E3 ligase, leading to inhibited cell proliferation and tumorigenicity. Our findings provide a novel perspective regarding circRNA function in physiological and pathological processes. Specifically, SHPRH-146aa generated from overlapping genetic codes of circ-SHPRH is a tumor suppressor in human glioblastoma.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The RTK/PI3K/AKT pathway plays key roles in the development and progression of many cancers, including GBM. As a regulatory molecule and a potential drug target, the oncogenic role of AKT has been ...substantially studied. Three isoforms of AKT have been identified, including AKT1, AKT2 and AKT3, but their individual functions in GBM remain controversial. Moreover, it is not known if there are more AKT alternative splicing variants.
High-throughput RNA sequencing and quantitative reverse transcription-PCR were used to identify the differentially expressed circRNAs in GBM samples and in paired normal tissues. High throughput RNA sequencing was used to identify circ-AKT3 regulated signaling pathways. Mass spectrometry, western blotting and immunofluorescence staining analyses were used to validate AKT3-174aa expression. The tumor suppressive role of AKT3-174aa was validated in vitro and in vivo. The competing interaction between AKT3-174aa and p-PDK1 was investigated by mass spectrometry and immunoprecipitation analyses.
Circ-AKT3 is a previously uncharacterized AKT transcript variant. Circ-AKT3 is expressed at low levels in GBM tissues compared with the expression in paired adjacent normal brain tissues. Circ-AKT3 encodes a 174 amino acid (aa) novel protein, which we named AKT3-174aa, by utilizing overlapping start-stop codons. AKT3-174aa overexpression decreased the cell proliferation, radiation resistance and in vivo tumorigenicity of GBM cells, while the knockdown of circ-AKT3 enhanced the malignant phenotypes of astrocytoma cells. AKT3-174aa competitively interacts with phosphorylated PDK1, reduces AKT-thr308 phosphorylation, and plays a negative regulatory role in modulating the PI3K/AKT signal intensity.
Our data indicate that the impaired circRNA expression of the AKT3 gene contributes to GBM tumorigenesis, and our data corroborate the hypothesis that restoring AKT3-174aa while inhibiting activated AKT may provide more benefits for certain GBM patients.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Aberrant activation of the Hedgehog pathway drives tumorigenesis of many cancers, including glioblastoma. However, the sensitization mechanism of the G protein-coupled-like receptor smoothened (SMO), ...a key component of Hedgehog signaling, remains largely unknown.
In this study, we describe a novel protein SMO-193a.a. that is essential for Hedgehog signaling activation in glioblastoma. Encoded by circular SMO (circ-SMO), SMO-193a.a. is required for sonic hedgehog (Shh) induced SMO activation, via interacting with SMO, enhancing SMO cholesterol modification, and releasing SMO from the inhibition of patched transmembrane receptors. Deprivation of SMO-193a.a. in brain cancer stem cells attenuates Hedgehog signaling intensity and suppresses self-renewal, proliferation in vitro, and tumorigenicity in vivo. Moreover, circ-SMO/SMO-193a.a. is positively regulated by FUS, a direct transcriptional target of Gli1. Shh/Gli1/FUS/SMO-193a.a. form a positive feedback loop to sustain Hedgehog signaling activation in glioblastoma. Clinically, SMO-193a.a. is more specifically expressed in glioblastoma than SMO and is relevant to Gli1 expression. Higher expression of SMO-193a.a. predicts worse overall survival of glioblastoma patients, indicating its prognostic value.
Our study reveals that SMO-193a.a., a novel protein encoded by circular SMO, is critical for Hedgehog signaling, drives glioblastoma tumorigenesis and is a novel target for glioblastoma treatment.
Abstract
Background
Triple negative breast cancer (TNBC) remains the most challenging breast cancer subtype so far. Specific therapeutic approaches have rarely achieved clinical improvements in ...treatment of TNBC patients and effective molecular biomarkers are largely unknown.
Methods
We used paired TNBC samples and high throughput RNA sequencing to identify differentially expressed circRNAs. Sucrose gradient polysome fractionation assay, antibody and Mass spectra were used to validate active circRNA translation. The novel protein function was validated in vitro and in vivo by gain or loss of function assays. Mechanistic results were concluded by immunoprecipitation analyses and kinase activity assay.
Results
Circular HER2 RNA (circ-HER2) encoded a novel protein, HER2–103. Unexpectedly, while HER2 mRNA and protein were barely detected, circ-HER2/HER2–103 was expressed in ~ 30% TNBC clinical samples. Circ-HER2/HER2–103 positive TNBC patients harbored worse overall prognosis than circ-HER2/HER2–103 negative patients. Knockdown circ-HER2 inhibited TNBC cells proliferation, invasion and tumorigenesis in vitro and in vivo, suggesting the critical role of circ-HER2/HER2–103 in TNBC tumorigenicity. Mechanistically, HER2–103 promoted homo/hetero dimerization of epidermal growth factor receptor (EGFR)/HER3, sustained AKT phosphorylation and downstream malignant phenotypes. Furthermore, HER2–103 shared most of the same amino acid sequences as HER2 CR1 domain which could be antagonized by Pertuzumab, a clinical used HER2 antibody. Pertuzumab markedly attenuated in vivo tumorigenicity of circ-HER2/HER2–103 expressing TNBC cells but showed no effects in circ-HER2/HER2–103 negative TNBC cells.
Conclusion
Our results not only demonstrated that certain TNBCs were not truly ‘HER2 negative’ but also highlighted the clinical implications of Pertuzumab in circ-HER2/HER2–103 expressing TNBC patients.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
miR-181a has been presumed to target the 3'-untranslated regions (3'-UTR) of IL1a based on software predictions. miR-181a and IL1a have opposite expression levels in monocytes and macrophages in the ...inflammatory state. This led us to suspect that mir-181a has an important function in regulating inflammatory response by targeting IL1a. Fluorescence reporter assays showed that miR-181a effectively binds to the 3'-UTR of IL1a. The anti-inflammatory functions of miR-181a were investigated in lipopolysaccharides (LPS)-induced Raw264.7 and phorbol 12-myristate 13-acetate (PMA)/LPS-induced THP-1 cells. We found that miR-181a mimics significantly lowered IL1a expression levels in these cells and, interestingly, miR-181a inhibitors reversed this decrease. In addition, miR-181a mimics significantly inhibited increase in the levels of inflammatory factors (IL1b, IL6, and TNFa) in these cells. Furthermore, miR-181a mimics and inhibitors decreased and increased, respectively, production of reactive oxygen species in PMA/LPS-induced THP-1 cells. These results indicate that miR-181a regulates inflammatory responses by directly targeting the 3'-UTR of IL1a and down-regulating IL1a levels. Interestingly, we found that miR-181a inhibited production of inflammatory factors even in IL1a-induced THP-1 cells, suggesting that the anti-inflammatory effects of miR-181a possibly involves other targets in addition to IL1a. Thus, we provide the first evidence for anti-inflammatory effects of miR-181a mediated at least in part by down-regulating IL1a.
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Circular RNAs and human glioma Liu, Jinglei; Zhao, Kun; Huang, Nunu ...
Cancer biology & medicine,
02/2019, Volume:
16, Issue:
1
Journal Article
Peer reviewed
Open access
As a newly discovered type of RNA, circular RNAs (circRNAs) are widespread throughout the eukaryotic genome. The expression of circRNAs is regulated by both cis-elements and trans-factors, and the ...expression pattern of circRNAs is cell type- and disease-specific. Similar to other types of non-coding RNAs, functions of circRNAs are also versatile. CircRNAs have been reported previously to function as microRNA (miRNA) sponges, protein sponges, coding RNAs or scaffolds for protein complexes. Recently, several circRNAs have been reported to play important roles in human malignancies, including glioma. Here, we reviewed several reports related to circRNAs and glioma, as well as the potential diagnostic and therapeutic applications of circRNAs in brain cancer. In general, some circRNAs, such as circSMARCA5 and circCFH, are found to be expressed in a glioma-specific pattern, these circRNAs may be used as tumor biomarkers. In addition, some circRNAs have been found to play oncogenic roles in glioma (e.g., circNFIX and circNT5E), whereas others have been reported to function as tumor suppressors (e.g., circFBXW7 and circSHPRH). Furthermore, circRNA is a good tool for protein expression because of its higher stability compared to linear RNAs. Thus, circRNAs may also be an ideal choice for gene/protein delivery in future brain cancer therapies. There are some challenges in circRNA research in glioma and other diseases. Research related to circRNAs in glioma is comparatively new and many mysteries remain to be solved.
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FFLJ, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, UL, UM, UPUK
Hypoxia activates autophagy, an evolutionarily conserved cellular catabolic process. Dysfunction in the autophagy pathway has been implicated in an increasing number of human diseases, including ...cancer. Hypoxia induces upregulation of a specific set of microRNAs (miRNAs) in a variety of cell types. Here, we describe hypoxia-induced MIR155 as a potent inducer of autophagy. Enforced expression of MIR155 increases autophagic activity in human nasopharyngeal cancer and cervical cancer cells. Knocking down endogenous MIR155 inhibits hypoxia-induced autophagy. We demonstrated that MIR155 targets multiple players in MTOR signaling, including RHEB, RICTOR, and RPS6KB2. MIR155 suppresses target-gene expression by directly interacting with their 3′ untranslated regions (UTRs), mutations of the binding sites abolish their MIR155 responsiveness. Furthermore, by downregulating MTOR signaling, MIR155 also attenuates cell proliferation and induces G
1
/S cell cycle arrest. Collectively, these data present a new role for MIR155 as a key regulator of autophagy via dysregulation of MTOR pathway.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
Activated by its single ligand, hepatocyte growth factor (HGF), the receptor tyrosine kinase MET is pivotal in promoting glioblastoma (GBM) stem cell self-renewal, invasiveness and tumorigenicity. ...Nevertheless, HGF/MET-targeted therapy has shown limited clinical benefits in GBM patients, suggesting hidden mechanisms of MET signalling in GBM. Here, we show that circular MET RNA (circMET) encodes a 404-amino-acid MET variant (MET404) facilitated by the N
-methyladenosine (m
A) reader YTHDF2. Genetic ablation of circMET inhibits MET404 expression in mice and attenuates MET signalling. Conversely, MET404 knock-in (KI) plus P53 knock-out (KO) in mouse astrocytes initiates GBM tumorigenesis and shortens the overall survival. MET404 directly interacts with the MET β subunit and forms a constitutively activated MET receptor whose activity does not require HGF stimulation. High MET404 expression predicts poor prognosis in GBM patients, indicating its clinical relevance. Targeting MET404 through a neutralizing antibody or genetic ablation reduces GBM tumorigenicity in vitro and in vivo, and combinatorial benefits are obtained with the addition of a traditional MET inhibitor. Overall, we identify a MET variant that promotes GBM tumorigenicity, offering a potential therapeutic strategy for GBM patients, especially those with MET hyperactivation.
Mol Cancer 18, 131 (2019) https://doi.org/10.1186/s12943-019-1056-5 Following publication of the original article 1, errors were identified in the images presented in Figs. 3 and 4; specifically: * ...Fig. 3C Representative images showing plate colony formations from different cell lines were incorrectly selected during figure assembly; this affects circ-AKT3 IRES mut U373 (bottom left in left-hand colony formations), and circ-AKT3 shRNA control SW1783 and HS683 (top and bottom left in right-hand colony formations). The correct representative images are now used * Fig. 4G Representative images of the control group for Empty Vector U373 (bottom left cell line) was incorrectly used. RAW_REF_TEXT Correction /RAW_REF_TEXT RAW_REF_TEXT Open Access /RAW_REF_TEXT RAW_REF_TEXT Published:07 June 2022 /RAW_REF_TEXT Correction: A novel tumor suppressor protein encoded by circular AKT3 RNA inhibits glioblastoma tumorigenicity by competing with active phosphoinositide-dependent Kinase-1 RAW_REF_TEXT Xin Xia1,2, /RAW_REF_TEXT RAW_REF_TEXT Xixi Li1,2, /RAW_REF_TEXT RAW_REF_TEXT Fanying Li1,2, /RAW_REF_TEXT RAW_REF_TEXT Xujia Wu1,2, /RAW_REF_TEXT RAW_REF_TEXT Maolei Zhang1,2, /RAW_REF_TEXT RAW_REF_TEXT Huangkai Zhou1,2, /RAW_REF_TEXT RAW_REF_TEXT Nunu Huang1,2, /RAW_REF_TEXT RAW_REF_TEXT Xuesong Yang1,2, /RAW_REF_TEXT RAW_REF_TEXT Feizhe Xiao3, /RAW_REF_TEXT RAW_REF_TEXT Dawei Liu4, /RAW_REF_TEXT RAW_REF_TEXT Lixuan Yang1,2 & /RAW_REF_TEXT RAW_REF_TEXT Nu Zhang 5,6 /RAW_REF_TEXT Molecular Cancer volume 21, Article number: 124 (2022) Cite this article RAW_REF_TEXT 181 Accesses /RAW_REF_TEXT RAW_REF_TEXT Metrics details /RAW_REF_TEXT The Original Article was published on 30 August 2019 Correction to: Mol Cancer 18, 131 (2019) https://doi.org/10.1186/s12943-019-1056-5 Following publication of the original article 1, errors were identified in the images presented in Figs. 3 and 4; specifically: RAW_REF_TEXT Fig. 3C Representative images showing plate colony formations from different cell lines were incorrectly selected during figure assembly; this affects circ-AKT3 IRES mut U373 (bottom left in left-hand colony formations), and circ-AKT3 shRNA control SW1783 and HS683 (top and bottom left in right-hand colony formations). The correct representative images are now used /RAW_REF_TEXT RAW_REF_TEXT Fig. 4G Representative images of the control group for Empty Vector U373 (bottom left cell line) was incorrectly used. Correction Open Access Published:07 June 2022 /RAW_REF_TEXT Correction: A novel tumor suppressor protein encoded by circular AKT3 RNA inhibits glioblastoma tumorigenicity by competing with active phosphoinositide-dependent Kinase-1 RAW_REF_TEXT Xin Xia1,2, Xixi Li1,2, Fanying Li1,2, Xujia Wu1,2, Maolei Zhang1,2, Huangkai Zhou1,2, Nunu Huang1,2, Xuesong Yang1,2, Feizhe Xiao3, Dawei Liu4, Lixuan Yang1,2 & Nu Zhang 5,6 /RAW_REF_TEXT Molecular Cancer volume 21, Article number: 124 (2022) Cite this article RAW_REF_TEXT 181 Accesses Metrics details /RAW_REF_TEXT The Original Article was published on 30 August 2019 Correction to: Mol Cancer 18, 131 (2019) https://doi.org/10.1186/s12943-019-1056-5 Following publication of the original article 1, errors were identified in the images presented in Figs. 3 and 4; specifically: RAW_REF_TEXT Fig. 3C Representative images showing plate colony formations from different cell lines were incorrectly selected during figure assembly; this affects circ-AKT3 IRES mut U373 (bottom left in left-hand colony formations), and circ-AKT3 shRNA control SW1783 and HS683 (top and bottom left in right-hand colony formations). The correct representative images are now used Fig. 4G Representative images of the control group for Empty Vector U373 (bottom left cell line) was incorrectly used.
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