Fig 4.

Entecavir, but not clevudine, could be used as a substrate to initiate protein priming. HP copurified with Hε was first incubated in TMgNK with 100 μM dGTP (lane 2), clevudine-TP (CLV-TP; lane 3), entecavir-TP (ETV-TP; lane 4), tenofovir DF-DP (TFV-DP; lane 5), or 3TC-TP (lane 6). To monitor dGTP (or analog)-independent (background) dATP incorporation, which could represent low-level misincorporation of dATP as the first nucleotide of priming (7), no dGTP was added to the reaction shown in lane 1 (control). Unincorporated nucleotides or analogs were then washed out, and fresh TMgNK buffer was added along with [α-³²P]dATP to allow DNA polymerization. After extensive washes to remove unincorporated nucleotides, samples were resolved by SDS-PAGE and visualized by autoradiography. The positions of the protein molecular mass markers (in kDa) are indicated.