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Circular RNA
In molecular biology, circular ribonucleic acid (or circRNA) is a type of single-stranded RNA which, unlike linear RNA, forms a covalently closed continuous loop. In circular RNA, the 3' and 5' ends normally present in an RNA molecule have been joined together. This feature confers numerous properties to circular RNA, many of which have only recently been identified.
Many types of circular RNA arise from otherwise protein-coding genes. Some circular RNA have been shown to code for proteins. Some types of circular RNA have also recently shown potential as gene regulators. The biological function of most circular RNA is unclear.
Because circular RNA do not have 5' or 3' ends, they are resistant to exonuclease-mediated degradation and are presumably more stable than most linear RNA in cells. Circular RNA has been linked to some diseases such as cancer.
In contrast to genes in bacteria, eukaryotic genes are split by non-coding sequences called introns. In eukaryotes, as a gene is transcribed from DNA into a messenger RNA (mRNA) transcript, intervening introns are removed, leaving only exons in the mature mRNA, which can subsequently be translated to produce the protein product. The spliceosome, a protein-RNA complex located in the nucleus, catalyzes splicing in the following manner:
Alternative splicing is a phenomenon through which one RNA transcript can yield different protein products based on which segments are considered "introns" and "exons" during a splicing event. Although not specific to humans, it is a partial explanation for the fact that humans and other much simpler species (such as nematodes) have similar numbers of genes (in the range of 20 - 25 thousand). One of the most striking examples of alternative splicing is in the Drosophila DSCAM gene, which can give rise to approximately 30 thousand distinct alternatively spliced isoforms.
Exon scrambling, also called exon shuffling, describes an event in which exons are spliced in a "non-canonical" (atypical) order. There are three ways in which exon scrambling can occur:
The notion that circularized transcripts are byproducts from imperfect splicing is supported by the low abundance and the lack of sequence conservation of most circRNAs, but has been challenged.
Repetitive Alu sequences represent approximately 10% of the human genome. The presence of Alu elements in flanking introns of protein-coding genes adjacent to the first and last exons that form circRNAs, influence the formation of circRNAs. It is important that the flanking intronic Alu elements are complementary, as this enables RNA pairing, which in turn facilitates circRNA synthesis.
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Circular RNA AI simulator
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Circular RNA
In molecular biology, circular ribonucleic acid (or circRNA) is a type of single-stranded RNA which, unlike linear RNA, forms a covalently closed continuous loop. In circular RNA, the 3' and 5' ends normally present in an RNA molecule have been joined together. This feature confers numerous properties to circular RNA, many of which have only recently been identified.
Many types of circular RNA arise from otherwise protein-coding genes. Some circular RNA have been shown to code for proteins. Some types of circular RNA have also recently shown potential as gene regulators. The biological function of most circular RNA is unclear.
Because circular RNA do not have 5' or 3' ends, they are resistant to exonuclease-mediated degradation and are presumably more stable than most linear RNA in cells. Circular RNA has been linked to some diseases such as cancer.
In contrast to genes in bacteria, eukaryotic genes are split by non-coding sequences called introns. In eukaryotes, as a gene is transcribed from DNA into a messenger RNA (mRNA) transcript, intervening introns are removed, leaving only exons in the mature mRNA, which can subsequently be translated to produce the protein product. The spliceosome, a protein-RNA complex located in the nucleus, catalyzes splicing in the following manner:
Alternative splicing is a phenomenon through which one RNA transcript can yield different protein products based on which segments are considered "introns" and "exons" during a splicing event. Although not specific to humans, it is a partial explanation for the fact that humans and other much simpler species (such as nematodes) have similar numbers of genes (in the range of 20 - 25 thousand). One of the most striking examples of alternative splicing is in the Drosophila DSCAM gene, which can give rise to approximately 30 thousand distinct alternatively spliced isoforms.
Exon scrambling, also called exon shuffling, describes an event in which exons are spliced in a "non-canonical" (atypical) order. There are three ways in which exon scrambling can occur:
The notion that circularized transcripts are byproducts from imperfect splicing is supported by the low abundance and the lack of sequence conservation of most circRNAs, but has been challenged.
Repetitive Alu sequences represent approximately 10% of the human genome. The presence of Alu elements in flanking introns of protein-coding genes adjacent to the first and last exons that form circRNAs, influence the formation of circRNAs. It is important that the flanking intronic Alu elements are complementary, as this enables RNA pairing, which in turn facilitates circRNA synthesis.