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Two genetic codes, one genome: Frameshifted primate mitochondrial genes code for additional proteins in presence of antisense antitermination tRNAs.
MedLine Citation:
PMID:  21669250     Owner:  NLM     Status:  Publisher    
Genomic amino acid usages coevolve with cloverleaf formation capacities of corresponding primate mitochondrial tRNAs, also for antisense tRNAs, suggesting translational function for sense and antisense tRNAs. Some antisense tRNAs are antitermination tRNAs (anticodons match stops (UAR: UAA, UAG; AGR: AGA, AGG)). Genomes possessing antitermination tRNAs avoid corresponding stops in frames 0 and +1, preventing translational antitermination. In frame +2, AGR stop frequencies and corresponding antisense antitermination tRNAs coevolve positively. This suggests expression of frameshifted overlapping genes, potentially shortening genomes, increasing metabolic efficiency. Blast analyses of hypothetical proteins translated between one and seven +1, respectively, +2 frameshifted human mitochondrial protein coding genes align with eleven GenBank sequences (31% of the mitochondrial coding regions). These putative overlap genes contain few UARs, AGRs align with arginine. Overlap gene numbers increase in presence of, and with time since evolution of antitermination tRNA AGR in 57 primate mitochondrial genomes. Numbers of putative proteins translated from antisense protein coding sequences and detected by blast also coevolve positively with antitermination tRNAs; expression of two of these 'antisense' mRNAs increases under low resource availability. Although more direct evidence is still lacking for the existence of proteins translated from overlapping mitochondrial genes and for antisense tRNAs activity, coevolutions between predicted overlap genes and the antitermination tRNAs required to translate them suggest expression of overlapping genes by an overlapping genetic code. Functions of overlapping genes remain unknown, perhaps originating from dual lifestyles of ancestral free living-parasitic mitochondria. Their amino acid composition suggests expression under anaerobic conditions.
Herve Seligmann
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-6-6
Journal Detail:
Title:  Bio Systems     Volume:  -     ISSN:  1872-8324     ISO Abbreviation:  -     Publication Date:  2011 Jun 
Date Detail:
Created Date:  2011-6-14     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0430773     Medline TA:  Biosystems     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2011. Published by Elsevier Ireland Ltd.
The National Collections of Natural History, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel; Center for Ecological and Evolutionary Synthesis, Department of Biological Sciences, University of Oslo, Blindern, N-0316 Oslo, Norway; Department of Life Sciences, Ben Gurion University, 84105 Beer Sheva, Israel.
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