Inhibition of MiniRT2 priming by RT domain fragments. Protein priming reactions were conducted in TMgNK using natively purified SUMO-MiniRT2 (1 pmol), in the presence of the indicated (GST-tagged) RT domain fragments (lanes 3 to 11) (32 pmol in panel A and 16 pmol in panel B). GST (lane 1) and the RT-YMHA mutant (lane 2) (32 pmol in panel A and 16 pmol in panel B) were used as negative and positive controls for trans-inhibition, respectively. The ε RNA was preincubated with MiniRT2 before the RT fragments were added. The protein priming signals are indicated in panel C as percentages of those without inhibition (i.e., in the presence of GST; lane 1). The means and standard errors are shown in the bar graph. Statistical significance was calculated using the one-tailed, unpaired Student t test. *, P < 0.05; **, P < 0.01; ***, P < 0.001.