Figure 2.

Imported tRNA is fragmented by mitochondrial 3′-exonuclease activity. (A) 5′-syntRNA^Tyr was labeled uniformly by in vitro transcription using α³²P-GTP (G), at the 5′-end by polynucleotide kinase and γ³²P-ATP (5′), or at the 3′-end by splint labeling using α³²P-ATP (3′) (Hausner et al., 1990; (Schneider et al., 1994). All substrates were tested in standard import reactions. (B) The size of the two sets of fragments have been calculated, and the regions of their estimated 3′-ends are indicated by arrows in the sequence of the 5′-syntRNA^Tyr.