Journal: Journal of Virology
Article Title: In Vitro Epsilon RNA-Dependent Protein Priming Activity of Human Hepatitis B Virus Polymerase
Figure Lengend Snippet: Differentiation of priming initiation from DNA polymerization by S1 nuclease digestion. (A) Protein priming was conducted with DP bound to M2 affinity beads in TMnNK buffer, in the presence of [α- 32 P]dGTP and unlabeled dCTP, dATP, and TTP. Priming products were either mock treated (−; lanes 5 and 6) or S1 treated (+; lanes 7 and 8), followed by mock treatment (−; lanes 5 and 7) or Tdp2 treatment (+; lanes 6 and 8), as described in Materials and Methods. Released nucleotides or DNAs were resolved by urea-PAGE and detected by autoradiography. The 10-nucleotide marker, the dTG, dTGA, and dTGAA DNA oligomers, and dGMP positions are indicated, as is the priming initiation product (I; i.e., the single dGMP residue released by Tdp2 from DP) or polymerization products (P; DNA polymerization from the first dGMP residue). (B) Protein priming was performed with DP in TMnNK buffer with [α- 32 P]dGTP (lanes 1 and 2) or with unlabeled dGTP (unlabled dNTP denoted by parentheses) followed by the addition of [α- 32 P]TTP to extend the unlabeled DP-dGMP initiation product (lanes 3 and 4). The priming products were then mock treated (−; lanes 1 and 3) or treated with S1 nuclease (+; lanes 2 and 4), resolved by SDS-PAGE, and detected by autoradiography. (C) Priming was performed with DP (lanes 1 and 2) or HP (lanes 3 to 6) in TMgNK buffer with [α- 32 P]dGTP (lanes 1 to 4) or with unlabeled dGTP first followed by addition of [α- 32 P]dATP to extend the unlabeled HP-dGMP initiation product (lanes 5 and 6). The priming products were either mock treated (−; lanes 1, 3, and 5) or S1 treated (+; lanes 2, 4, and 6), resolved by SDS-PAGE, and detected by autoradiography. (D) The percent decreases in DP and HP priming signals as a result of S1 nuclease treatment are represented. Mock-treated DP initiation reaction in the presence of [α- 32 P]dGTP alone, with either TMnNK or TMgNK buffer, was set as 100%, and the other reaction conditions, as explained in panels B and C, were normalized to this. The decrease in priming signal due to proteolytic degradation (unrelated to S1 nuclease cleavage of internucleotide linkages) was subtracted from the calculations. (E) DP or HP was incubated with or without S1 nuclease as described above. Protease degradation was monitored by Western blotting using the M2 anti-Flag antibody. HC, antibody heavy chain. The symbol * in panels B, C, and E represents DP and HP degradation products caused by contaminating protease activity in S1. Note that only some proteolytic degradation products detected by the Western blot (E) appeared to match the 32 P-labeled degradation products (B and C) since the labeled products must have contained the priming site(s), whereas the Western blot detected only fragments containing the N-terminal FLAG tag. Also, some labeled degradation products might be present at such low levels that they were undetectable by Western blotting. Note also that the appearance of the proteolytic degradation products was accompanied by the decrease of the full-length HP or DP in panels B, C, and E. (F) The diagram depicts the cleavage of the internucleotide linkages, but not the HP-dGMP linkage, by S1.
Article Snippet: One microliter of [α-32 P]dGTP (10 mCi/ml [3,000 Ci/mmol]; PerkinElmer) was then added, and the reaction mixtures were incubated at 25°C for 4 h with shaking.
Techniques: Polyacrylamide Gel Electrophoresis, Autoradiography, Marker, SDS Page, Incubation, Western Blot, Activity Assay, Labeling, FLAG-tag