Circular RNAs exhibit limited evidence for translation, or translation regulation of the mRNA-counterpart in terminal hematopoiesis
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ABSTRACT:
ORGANISM(S): Homo sapiens
PROVIDER: GSE159579 | GEO | 2021/03/04
REPOSITORIES: GEO
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Project description:Each day, about 1012 erythrocytes and platelets are released into the bloodstream. This substantial output from hematopoietic stem cells is tightly regulated by transcriptional and epigenetic factors. Whether and how circular RNAs (circRNAs) contribute to the differentiation and/or identity of hematopoietic cells is to date not known. We recently reported that erythrocytes and platelets contain the highest levels and numbers of circRNAs among hematopoietic cells. Here, we provide the first detailed analysis of circRNA expression during erythroid and megakaryoid differentiation. CircRNA expression not only significantly increased upon enucleation, but also had limited overlap between progenitor cells and mature cells, suggesting that circRNA expression stems from regulated processes rather than resulting from mere accumulation. To study circRNA function in hematopoiesis, we first compared the expression levels of circRNAs with the translation efficiency of their mRNA counterpart. We found that only one out of 2531 (0.04%) circRNAs associated with mRNA-translation regulation. Furthermore, irrespective of thousands of identified putative open reading frames, deep ribosome-footprinting sequencing, and mass spectrometry analysis provided little evidence for translation of endogenously expressed circRNAs. In conclusion, circRNAs alter their expression profile during terminal hematopoietic differentiation, yet their contribution to regulate cellular processes remains enigmatic.
| S-EPMC8906552 | biostudies-literature
Project description:Circular RNAs exhibit limited evidence for translation, or translation regulation of the mRNA-counterpart in terminal hematopoiesis
| PRJNA669808 | ENA
Project description:Erythrocytes and platelets have high production rates, with 1012 cells released daily into the blood stream. This output from bone-marrow residing hematopoietic stem cells is tightly regulated by transcription factors and epigenetic modifications. Whether and how non-coding RNAs such as circular RNAs (circRNAs) contribute to the differentiation and/or identity of hematopoietic cells is to date not well understood. We recently published a circRNA expression map of hematopoietic cells, which showed that erythrocytes and platelets contain the highest levels and numbers of circRNAs. Whether and how circRNA expression alters during differentiation of erythrocytes and platelet precursors is however not known. Therefore, we here provide the first detailed and comprehensive analysis of circRNA expression during red blood cell and megakaryocyte differentiation. CircRNA expression significantly increased during erythroid precursor differentiation into red blood cells, and in differentiating megakaryocytes, in particular upon enucleation. Many functions have been attributed to circRNAs. To dissect their possible function in hematopoietic differentiation, we first focused on translation regulation. We compared circRNA and mRNA expression to ribosomal foot printing data, and found that only 20 (2.6%) circRNAs associated with translation regulation of their mRNA counterparts. We also identified thousands of putative open reading frames in circRNAs, suggesting that circRNAs may also encode proteins. However, deep ribosome-footprinting sequencing data and in-depth mass spectrometry data analysis provided little evidence for translation of endogenously expressed circRNAs in erythroblasts, megakaryocytes and platelets. In conclusion, circRNAs in platelets and red blood cells are highly abundant and alter their expression profile during differentiation, yet their contribution to regulate cellular processes remains enigmatic.
2021-03-04 | GSE159578 | GEO
Project description:Erythrocytes and platelets have high production rates, with 1012 cells released daily into the blood stream. This output from bone-marrow residing hematopoietic stem cells is tightly regulated by transcription factors and epigenetic modifications. Whether and how non-coding RNAs such as circular RNAs (circRNAs) contribute to the differentiation and/or identity of hematopoietic cells is to date not well understood. We recently published a circRNA expression map of hematopoietic cells, which showed that erythrocytes and platelets contain the highest levels and numbers of circRNAs. Whether and how circRNA expression alters during differentiation of erythrocytes and platelet precursors is however not known. Therefore, we here provide the first detailed and comprehensive analysis of circRNA expression during red blood cell and megakaryocyte differentiation. CircRNA expression significantly increased during erythroid precursor differentiation into red blood cells, and in differentiating megakaryocytes, in particular upon enucleation. Many functions have been attributed to circRNAs. To dissect their possible function in hematopoietic differentiation, we first focused on translation regulation. We compared circRNA and mRNA expression to ribosomal foot printing data, and found that only 20 (2.6%) circRNAs associated with translation regulation of their mRNA counterparts. We also identified thousands of putative open reading frames in circRNAs, suggesting that circRNAs may also encode proteins. However, deep ribosome-footprinting sequencing data and in-depth mass spectrometry data analysis provided little evidence for translation of endogenously expressed circRNAs in erythroblasts, megakaryocytes and platelets. In conclusion, circRNAs in platelets and red blood cells are highly abundant and alter their expression profile during differentiation, yet their contribution to regulate cellular processes remains enigmatic.
2021-03-04 | GSE159577 | GEO
Project description:Most of the eukaryotic genome is pervasively transcribed, yielding hundreds to thousands of long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs), some of which are well conserved during evolution. Functions have been described for a few lncRNAs and circRNAs but remain elusive for most. Both classes of RNAs play regulatory roles in translation by interacting with messenger RNAs (mRNAs), microRNAs (miRNAs), or mRNA-binding proteins (RBPs), thereby modulating translation in trans Moreover, although initially defined as noncoding, a number of lncRNAs and circRNAs have recently been reported to contain functional open reading frames (ORFs). Here, we review current understanding of the roles played by lncRNAs and circRNAs in protein synthesis and discuss challenges and open questions in the field.
| S-EPMC6546045 | biostudies-literature
Project description:Extensive pre-mRNA back-splicing generates numerous circular RNAs (circRNAs) in human transcriptome. However, the biological functions of these circRNAs remain largely unclear. Here we report that N6-methyladenosine (m6A), the most abundant base modification of RNA, promotes efficient initiation of protein translation from circRNAs in human cells. We discover that consensus m6A motifs are enriched in circRNAs and a single m6A site is sufficient to drive translation initiation. This m6A-driven translation requires initiation factor eIF4G2 and m6A reader YTHDF3, and is enhanced by methyltransferase METTL3/14, inhibited by demethylase FTO, and upregulated upon heat shock. Further analyses through polysome profiling, computational prediction and mass spectrometry reveal that m6A-driven translation of circRNAs is widespread, with hundreds of endogenous circRNAs having translation potential. Our study expands the coding landscape of human transcriptome, and suggests a role of circRNA-derived proteins in cellular responses to environmental stress.
| S-EPMC5520850 | biostudies-other
Project description:Circular RNAs (circRNAs) are a new class of non-coding RNAs formed by covalently closed loops through backsplicing. Recent methodologies have enabled in-depth characterization of circRNAs for identification and potential functions. CircRNAs play important roles in various biological functions as microRNA sponges, transcriptional regulators and combining with RNA binding proteins. Recent studies indicated that some cytoplasmic circRNAs can be effectively translated into detectable peptides, which enlightened us on the importance of circRNAs in cellular physiology function. Internal Ribosome Entry site (IRES)- and N6-methyladenosines (m6A)-mediated cap-independent translation initiation have been suggested to be potential mechanism for circRNA translation. To date, several translated circRNAs have been uncovered to play pivotal roles in human cancers. In this review, we introduced the properties and functions of circRNAs, and characterized the possible mechanism of translation initiation and complexity of the translation ability of circRNAs. We summarized the emerging functions of circRNA-encoded proteins in human cancer. The works on circRNA translation will open a hidden human proteome, and enhance us to understand the importance of circRNAs in human cancer, which has been poorly explored so far.
| S-EPMC7023758 | biostudies-literature
Project description:Circular RNAs (circRNAs) encompass a widespread and conserved class of RNAs, which are generated by back-splicing of downstream 5' to upstream 3' splice sites. CircRNAs are tissue-specific and have been implicated in diseases including cancer. They can function as sponges for microRNAs (miRNAs) or RNA binding proteins (RBPs), for example. Moreover, some contain open reading frames (ORFs) and might be translated. The functional relevance of such peptides, however, remains largely elusive. Here, we report that the ORF of circZNF609 is efficiently translated when expressed from a circZNF609 overexpression construct. However, endogenous proteins could not be detected. Moreover, initiation of circZNF609 translation is independent of m6A-generating enzyme METTL3 or RNA sequence elements such as internal ribosome entry sites (IRESs). Surprisingly, a comprehensive mutational analysis revealed that deletion constructs, which are deficient in producing circZNF609, still generate the observed protein products. This suggests that the apparent circZNF609 translation originates from trans-splicing by-products of the overexpression plasmids and underline that circRNA overexpression constructs need to be evaluated carefully, particularly when functional studies are performed.
| S-EPMC7544230 | biostudies-literature
Project description:Circular RNAs (circRNAs) constitute a recently recognized group of noncoding transcripts that function as posttranscriptional regulators of gene expression at a new level. Recent developments in experimental methods together with rapidly evolving bioinformatics approaches have accelerated the exploration of circRNAs. The differentiation of hematopoietic stem cells into a broad spectrum of specialized blood lineages is a tightly regulated process that depends on a multitude of factors, including circRNAs. However, despite the growing number of circRNAs described to date, the roles of the majority of them in hematopoiesis remain unknown. Given their stability and disease-specific expression, circRNAs have been acknowledged as novel promising biomarkers and therapeutic targets. In this paper, the biogenesis, characteristics, and roles of circRNAs are reviewed with an emphasis on their currently recognized or presumed involvement in hematopoiesis, especially in acute myeloid leukemia and myelodysplastic syndrome.
| S-EPMC7503587 | biostudies-literature
Project description:Some circular RNAs (circRNAs) were found to be translated through IRES-driven mechanism, however the scope and functions of circRNA translation are unclear because endogenous IRESs are rare. To determine the prevalence and mechanism of circRNA translation, we develop a cell-based system to screen random sequences and identify 97 overrepresented hexamers that drive cap-independent circRNA translation. These IRES-like short elements are significantly enriched in endogenous circRNAs and sufficient to drive circRNA translation. We further identify multiple trans-acting factors that bind these IRES-like elements to initiate translation. Using mass-spectrometry data, hundreds of circRNA-coded peptides are identified, most of which have low abundance due to rapid degradation. As judged by mass-spectrometry, 50% of translatable endogenous circRNAs undergo rolling circle translation, several of which are experimentally validated. Consistently, mutations of the IRES-like element in one circRNA reduce its translation. Collectively, our findings suggest a pervasive translation of circRNAs, providing profound implications in translation control.
| S-EPMC9242994 | biostudies-literature