Figure 1.

Sequences used in this study. Only the nontemplate strand is shown (5′-3′). The sequence CG₁₄ is a Z-DNA forming sequence. The palindromic sequence PD was obtained from the sequence CG₁₄ by three G-C permutations (bold, underlined) symmetrical relative to the center of the sequence (shown by a small arrow). The irregular sequence CON was used previously as a control in studies of Z-DNA induced mutagenesis (29), and the sequence TRANS was previously shown to have no effect on transcription elongation (unpublished data) and thus was used as a negative control.