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. 2017 Oct;23(10):1539–1551. doi: 10.1261/rna.061796.117

FIGURE 2.

FIGURE 2.

The importance of the J1/4 region for the SAM-I riboswitch transcriptional activity. (A) Schematic representing the secondary structure of the SAM-I riboswitch aptamer. The location of residues 114, 136, 137, and 138 is shown using black circles. The tertiary interaction occurring between positions 114 and 138 is shown by a dotted line. (B) Single-round in vitro transcriptions performed in the absence (−) or in the presence of 1 µM SAM for the wild-type and selected J1/4 riboswitch mutants. Readthrough (R) and prematurely terminated (T) transcripts are indicated on the right and percentages of termination (%T) are shown below the gel. (C,D) Single-round in vitro transcriptions performed as a function of SAM concentration for the wild-type (C) and the U114A:A138U (D) riboswitch mutant. Terminated and readthrough products are indicated on the right. SAM concentrations correspond to 10 pM, 100 pM, 1 nM, 5 nM, 10 nM, 50 nM, 100 nM, 500 nM, 1 µM, 5 µM, 10 µM, and 100 µM. (E) Quantification analysis of single-round in vitro transcriptions shown in C and D. The relative termination ratios are reported for the wild-type (black circles) and the U114A:A138U (white circles) riboswitch mutant.