S1 nuclease protection of shorter RNAs associated
with stalled transcription complexes. (A) Schematic diagram
of RNAs synthesized under limiting nucleotide concentrations in
isolated mitochondria and S1 nuclease protection of the resulting RNA
species. (B and C) S1 nuclease protection
of labeled RNAs with unlabeled ssDNA corresponding to edited
coI sequence (probe 1). (B) Lane 1, edited
coI control transcript; lanes 2–5, RNAs synthesized in
isolated mitochondria during a 3-min pulse labeling in the presence of
limiting (radiolabeled) ATP, CTP, GTP, or UTP. (C) Lane 1,
edited coI control transcript; lanes 2–5, RNAs
synthesized in isolated mitochondria. Lanes: 2, 3-min pulse labeling,
limiting GTP; 3, 15-min pulse labeling, limiting GTP; 4, 3-min pulse
labeling, limiting GTP, followed by a 12 min chase with 100 μM GTP;
5, 3-min pulse labeling, limiting GTP, followed by a 12 min chase with
100 μM UTP.