FIG. 3.

Analysis of short G6 transcripts initiated at wild-type and mutant upp promoters. DNA templates containing either the wild-type (T₈) or a T_n mutant promoter were transcribed in vitro in reaction mixtures containing 200 μM each ATP, CTP, and [γ-³²P]GTP and 50 μM UTP. The autoradiograph is of the 25% polyacrylamide gel used to separate the transcripts. The numbers on the left indicate transcript length (in nucleotides); brackets are used to indicate equal-length transcripts with different sequences, which in most cases cause these transcripts to migrate differently in the gel. In the case of the wild-type promoter (i.e., lane T₈ only), several other transcripts are marked. Transcripts with the sequences GAU₉ and GAU₈G are labeled. Two longer GAU_n transcripts (i.e., GAU₁₀ and GAU₁₁) are marked with asterisks. The longest unambiguously assigned product of simple abortive initiation, GAU₈GU, is marked with a diamond.