Fig 3.

Determination of priming site usage in cis- and trans-priming by alkaline treatment of the priming products. Priming reactions were carried out in TMnNK (lanes 1 to 4, 6, and 8) or TMgNK (lanes 5 and 7), using SUMO-MiniRT2 (lanes 1 to 4), GST-RT (lanes 5 to 8), His-RT (lane 2), His-TP (lanes 3, 5, and 6), or His-TP-Y96F (lanes 4 and 8). The reaction products were resolved by SDS-PAGE. The gel was then cut into two parts; one part, containing one set of the priming reaction products, was mock treated (top panel), and the other part, containing a second set of the same priming reaction products, was treated with 3 M KOH (bottom panels). The priming products were then detected by autoradiography. Lanes 9 to 16 represent a longer exposure of lanes 1 to 8 of the bottom panel.