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CO2-sensitive tRNA modification associated with human mitochondrial disease.

Nature communications (2018-05-16)
Huan Lin, Kenjyo Miyauchi, Tai Harada, Ryo Okita, Eri Takeshita, Hirofumi Komaki, Kaoru Fujioka, Hideki Yagasaki, Yu-Ichi Goto, Kaori Yanaka, Shinichi Nakagawa, Yuriko Sakaguchi, Tsutomu Suzuki
ABSTRACT

It has been generally thought that tRNA modifications are stable and static, and their frequencies are rarely regulated. N6-threonylcarbamoyladenosine (t6A) occurs at position 37 of five mitochondrial (mt-)tRNA species. We show that YRDC and OSGEPL1 are responsible for t6A37 formation, utilizing L-threonine, ATP, and CO2/bicarbonate as substrates. OSGEPL1-knockout cells exhibit respiratory defects and reduced mitochondrial translation. We find low level of t6A37 in mutant mt-tRNA isolated from the MERRF-like patient's cells, indicating that lack of t6A37 results in pathological consequences. Kinetic measurements of t6A37 formation reveal that the Km value of CO2/bicarbonate is extremely high (31 mM), suggesting that CO2/bicarbonate is a rate-limiting factor for t6A37 formation. Consistent with this, we observe a low frequency of t6A37 in mt-tRNAs isolated from human cells cultured without bicarbonate. These findings indicate that t6A37 is regulated by sensing intracellular CO2/bicarbonate concentration, implying that mitochondrial translation is modulated in a codon-specific manner under physiological conditions.

MATERIALS
Product Number
Brand
Product Description

Millipore
ANTI-FLAG® M2 Affinity Gel, purified immunoglobulin, buffered aqueous glycerol solution
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Dulbecco′s Modified Eagle′s Medium - high glucose, With 4500 mg/L glucose, L-glutamine, and sodium bicarbonate, without sodium pyruvate, liquid, sterile-filtered, suitable for cell culture
Sigma-Aldrich
Dulbecco′s Modified Eagle′s Medium - high glucose, With 4500 mg/L glucose and L-glutamine, without sodium bicarbonate, powder, suitable for cell culture
Sigma-Aldrich
Anti-OSGEPL1 antibody produced in rabbit, Prestige Antibodies® Powered by Atlas Antibodies, affinity isolated antibody, buffered aqueous glycerol solution