FIGURE 3.

Gel assay of processivity of cDNA synthesis. A 807-nt in vitro transcript containing an Ll.LtrB-ΔORF group II intron RNA with a 5′-³²P-labeled primer annealed near its 3′ end was incubated for 30 min with TeI4c-MRF (2 μM) or GsI-IIc-MRF (1 μM) at 60°C or SuperScript III (10 units/μL) at 55°C in the presence of excess poly(rA)/oligo (dT)₄₂ as a trap, and the products were analyzed in a denaturing 6% polyacrylamide gel alongside a 5′-labeled 10-bp ladder (M). The processivity (average length of template copied per initiation) was calculated by using the equation Σ(L_n.I_n)/Σ(I_n), where L_n is the length and I_n is the intensity of each analyzed cDNA fragment.