Figure 3.

Characterization of TEC. (A) Dot blot hybridization analysis of RNAs synthesized by TEC. DNAs from the nuclear genes actin and tubulin, the mitochondrial genes coI, coII and α-ATPase, and the cloning vector were immobilized and hybridized to labeled transcripts synthesized by TEC as described in Materials and Methods. (B) RNase H digestion of S1 nuclease protected α-ATPase mRNA synthesized in the absence of a cold nucleotide chase. Lane 1, no oligonucleotide, no RNase H; lane 2, oligonucleotide A in the presence of RNase H; lane 3, oligonucleotide B in the presence of RNase H. Sizes of the expected cleavage products are shown in the diagram to the right. (C) Nucleotide requirements for transcription by TEC. Run-on RNA synthesis in the presence of all four ribonucleotides (lane 1); 20 µM [α-³²P]UTP only (lane 2); 20 µM [α-³²P]UTP, 500 µM CTP and GTP (lane 3); 20 µM [α-³²P]UTP and 500 µM ATP and GTP (lane 4); or 20 µM [α-³²P]UTP and 500 µM CTP and ATP (lane 5).