Intragenic regions (introns) are found in all classes of organism. Transcription of such genes must undergo a splicing reaction to produce the mature, functional form of RNAs. Introns can be divided into four categories by their splicing mechanisms, namely Group I, Group II, spliceosomal, and nuclear tRNA introns. The former two are self-splicing introns. Group I introns are ubiquitous, however, most metazoan mitochondrial genomes lack introns. A novel group I intron in the mitochondrial cytochrome oxidase I gene (cox1) of Cinachyrella auctraliensis, which belongs to the IB2 subgroup, encodes a putative homing endonuclease with two amino acid motifs of the LAGLIDADG family. The homing endonuclease may perform intron translocation. Splicing in the cox1 of the sponge was demonstrated by comparing the length of DNA and RNA sequences. The intron was spliced in vivo or in vitro as revealed by RT-PCR and sequencing. Group I introns are classified as ribozymes. The pre-mRNAs fold into specific configurations that facilitate attacks of free guanosine followed by two consecutive trans-esterification steps to remove the introns. The excised cox1 intron was found to form a circle with the 5¡¦-end linked to the 3¡¦-end. Two other forms of lariats were also found with the 5¡¦-end linked to the inside sequence of the intron. Mutagenesis of a key nucleotide, which participates base pairing of RNA secondary structure, in P7 region decreased the splicing activity of the intron.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0819109-130742 |
| Date | 19 August 2009 |
| Creators | Chan, Hui-mei |
| Contributors | Chi-Hsin Hsu, Chan-Shing Lin, Zhi-Hong Wen |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | Cholon |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0819109-130742 |
| Rights | not_available, Copyright information available at source archive |
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