Circularization of DNA templates (COLIGOs) for Rolling Circle Transcription. A . Synthetic 5′ phosphorylated linear DNA sequences were circularized using the thermostable TS2126 RNA ligase. B . Denaturing polyacrylamide gel electrophoresis (DPAGE) at four stages during miR-19am DNA circle synthesis. Lane 1, crude DNA IDT Ultramer synthesis of COLIGO 19am. Lane 2, after preparative DPAGE. Lane 3, crude circularization product. Lane 4, DNA circle template following <t>Exonuclease</t> I clean-up. Visualization using Stains-All. C . Verification of circular topology. Nicking of circular templates by S1 nuclease leads first to linear forms, which are then further digested to successively smaller linear forms.