B. Franz Lang, Michaela Jakubkova, Eva Hegedusova, Rachid Daoud, Lise Forget, Brona Brejova, Tomas Vinar, Peter Kosa, Dominika Fricova, Martina Nebohacova, Peter Griac, Lubomir Tomaska, Gertraud Burger, Jozef Nosek. Massive programmed translational jumping in mitochondria. Proceedings of the National Academy of Sciences of the United States of America, 111(16):5926-5931. 2014.

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Programmed translational bypassing is a process whereby ribosomes 'ignore' a
substantial interval of mRNA sequence. Although discovered 25 y ago, the only
experimentally confirmed example of this puzzling phenomenon is expression of the
bacteriophage T4 gene 60. Bypassing requires translational blockage at a 'takeoff
codon' immediately upstream of a stop codon followed by a hairpin, which causes
peptidyl-tRNA dissociation and reassociation with a matching 'landing triplet' 50
nt downstream, where translation resumes. Here, we report 81 translational
bypassing elements (byps) in mitochondria of the yeast Magnusiomyces capitatus
and demonstrate in three cases, by transcript analysis and proteomics, that byps 
are retained in mitochondrial mRNAs but not translated. Although mitochondrial
byps resemble the bypass sequence in the T4 gene 60, they utilize unused codons
instead of stops for translational blockage and have relaxed matching rules for
takeoff/landing sites. We detected byp-like sequences also in mtDNAs of several
Saccharomycetales, indicating that byps are mobile genetic elements. These
byp-like sequences lack bypassing activity and are tolerated when inserted
in-frame in variable protein regions. We hypothesize that byp-like elements have 
the potential to contribute to evolutionary diversification of proteins by adding
new domains that allow exploration of new structures and functions.

Last update: 08/12/2014