title: Shifting constraints on tRNA genes during mitochondrial DNA evolution in animals.
abstract: During the evolution of echinoderm mitochondrial (mt) DNA, a transfer RNA gene lost its tRNA function and became part of a protein-coding gene. To examine the evolutionary consequences of this event, we sequenced 961 bp of mtDNA in five sea urchin species. This enabled us to build a tree relating the mtDNAs and use it for analyzing the pattern and process of evolutionary substitutions in the former leucine tRNA gene, which now is a 5' extension of the gene for NADH dehydrogenase subunit 5 (ND5). This 5' extension is now evolving at the same rate and under the same protein-coding constraints as the rest of ND5. The adjacent (upstream) serine tRNA gene, however, has been evolving at a reduced rate, consistent with the possibility that it has assumed a punctuation role in processing of the primary transcript that was once fulfilled by the former leucine tRNA gene.
authors.affiliation: Division of Biochemistry and Molecular Biology, University of California, Berkeley 94720.
authors.forename: W K
authors.initials: WK
authors.lastname: Thomas
authors.forename: J
authors.initials: J
authors.lastname: Maa
authors.forename: A C
authors.initials: AC
authors.lastname: Wilson
mesh_terms: D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D004272:DNA, Mitochondrial / Q000235:genetics*; D005796:Genes; D014644:Genetic Variation; D008969:Molecular Sequence Data; D009245:NADH Dehydrogenase / Q000235:genetics; D010802:Phylogeny; D012323:RNA Processing, Post-Transcriptional; D012343:RNA, Transfer / Q000235:genetics*; D012356:RNA, Transfer, Leu / Q000235:genetics; D012362:RNA, Transfer, Ser / Q000235:genetics; D012045:Regulatory Sequences, Nucleic Acid; D012617:Sea Urchins / Q000145:classification / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D013045:Species Specificity
chemical_list: D004272:DNA, Mitochondrial; D012356:RNA, Transfer, Leu; D012362:RNA, Transfer, Ser; D012343:RNA, Transfer; D009245:NADH Dehydrogenase