Fig. 2.

Nucleus-encoded tRNA^Gln is imported into rat and human mitochondria. (A) RT-PCR with primers specific for the nucleus-encoded tRNA^Gln (ntRNA^Gln) isoacceptors and total RNA isolated from rat (Left) or human (Right) mitochondria. These primers are unable to amplify the endogenous mitochondria-encoded tRNA_UUG^Gln (mttRNA_UUG^Gln) and can only discriminate between four of the possible six nucleus-encoded isoacceptors. (B) Similar RT-PCR as in A but with extramitochondrial RNA, which includes a mixture of cytoplasmic as well as nuclear RNA generated from the same preparation as that used to isolate the mitochondria in A. (C) RT-PCR with U6-specific oligonucleotides (extramitochondrial marker) with the same RNA fractions as in A and B. RT+ and RT− refer to cDNA synthesis reactions performed in the presence or absence of reverse transcriptase, respectively. No template is a mock reaction in which no cDNA was added, also serving as a negative control. Mito, RNA isolated from purified mitochondria. M, a 100-bp DNA ladder used as size markers during electrophoresis.