| dc.contributor.author | Bullerwell, Charles Edward. | en_US |
| dc.date.accessioned | 2014-10-21T12:33:32Z | |
| dc.date.available | 2005 | |
| dc.date.issued | 2005 | en_US |
| dc.identifier.other | AAINR00962 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/54691 | |
| dc.description | In the chytridiomycete fungus Spizellomyces punctatus , all eight of the tRNAs encoded in the mitochondrial genome are predicted to have one or more base pair mismatches at the first three positions of their aminoacyl acceptor stems. These tRNAs are edited post-transcriptionally by replacement of the 5' nucleotide in each mismatched pair with a nucleotide that can form a standard Watson-Crick base pair with its counterpart in the 3' half of the stem. The type of mitochondrial tRNA editing found in S. punctatus also occurs in Acanthamoeba castellanii, a distantly related amoeboid protist. Using an S. punctatus mitochondrial extract, I developed an in vitro assay of tRNA editing in which nucleotides are incorporated into various tRNA substrates. Experiments employing synthetic transcripts revealed that the S. punctatus tRNA editing activity incorporates nucleotides on the 5' side of substrate tRNAs, uses the 3' sequence as a template for incorporation, and adds nucleotides in a 3'-to-5' direction. This activity can add nucleotides to a triphosphorylated 5 ' end in the absence of ATP but requires ATP to add nucleotides to a monophosphorylated 5' end; moreover, it functions independently of the state of tRNA 3' processing. These data parallel results obtained here and in a previous in vitro study of A. castellanii tRNA editing, suggesting that remarkably similar activities function in the mitochondria of these two organisms. The evolutionary origins of these activities are discussed. | en_US |
| dc.description | In the course of this work I discovered two small RNAs, one in mitochondrial RNA preparations from A. castellanii and the other in mitochondrial RNA preparations from the related amoeba Hartmannella vermiformis . Each of these RNAs has properties expected of a mitochondrial 5S rRNA, and each is mitochondrially encoded. These findings were unexpected, as analysis of the complete mitochondrial genome sequences from these two organisms had previously failed to reveal a 5S rRNA gene. These results emphasize the limitations of gene prediction based solely on DNA sequence, and at the same time suggest that the requirement for a 5S rRNA component in mitochondrial ribosomes is more stringent than previously believed. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 2005. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Biology, Molecular. | en_US |
| dc.subject | Chemistry, Biochemistry. | en_US |
| dc.title | tRNA editing and characterization of novel small RNAs in protist mitochondria. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
