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Within introns, a donor site (5' end of the intron), a branch site (near the 3' end of the intron) and an acceptor site (3' end of the intron) are required for splicing. The splice donor site includes an almost invariant sequence GU at the 5' end of the intron, within a larger, less highly conserved region.
Splice site mutation. A splice site mutation is a genetic mutation that inserts, deletes or changes a number of nucleotides in the specific site at which splicing takes place during the processing of precursor messenger RNA into mature messenger RNA. Splice site consensus sequences that drive exon recognition are located at the very termini of ...
Alternative splicing produces three protein isoforms. Protein A includes all of the exons, whereas Proteins B and C result from exon skipping. Alternative splicing, or alternative RNA splicing, or differential splicing, is an alternative splicing process during gene expression that allows a single gene to produce different splice variants.
The 5' splice site sequence is then subjected to a nucleophilic attack by a downstream sequence called the branch point, resulting in a circular structure called a lariat. The free 5' exon then attacks the 3' splice site, joining the two exons and releasing a structure known as an intron lariat. The intron lariat is subsequently de-branched and ...
Splicing of group I introns is processed by two sequential transesterification reactions. [3] First an exogenous guanosine or guanosine nucleotide (exoG) docks onto the active G-binding site located in P7, and then its 3'-OH is aligned to attack the phosphodiester bond at the "upstream" (closer to the 5' end) splice site located in P1, resulting in a free 3'-OH group at the upstream exon and ...
The outron is an intron-like sequence possessing similar characteristics such as the G+C content [3] and a splice acceptor site that is the signal for trans-splicing. [4] [5] Such a trans-splice site is essentially defined as an acceptor (3') splice site without an upstream donor (5') splice site.
Trans-splicing is characterized by the joining of two separate exons transcribed RNAs. The signal for this splicing is the outron at the 5’ end of the mRNA, in the absence of a functional 5’ splice site upstream. When the 5’ outron in spliced, the 5’ splice site of the spliced leader RNA is branched to the outron and forms an ...
An internal ribosome entry site, abbreviated IRES, is an RNA element that allows for translation initiation in a cap-independent manner, as part of the greater process of protein synthesis. Initiation of eukaryotic translation nearly always occurs at and is dependent on the 5' cap of mRNA molecules, where the translation initiation complex ...