FIGURE 4.

The isolated exonuclease and RQC domains of WRN stimulate hpol η^1–437 activity. A, DNA synthesis by hpol η^1–437 (2 nm) was monitored over time in the presence of the 100 nm (■) WRN^1–333 exonuclease domain. The no WRN control experiment (●) from Fig. 1 was re-plotted for comparison. Formation of total product is shown. The single turnover results for each experiment were fit to a single exponential equation to yield the following kinetic parameters: WRN^1–333 (■): A = 181 ± 3 nm, k_obs = 0.44 ± 0.03 min⁻¹. B, DNA synthesis by hpol η^1–437 (2 nm) was monitored over time in the presence of 100 nm (■) and 1 μm (▴) WRN^949–1078 RQC domain. The no WRN control experiment (●) from Fig. 1 was re-plotted for comparison. Formation of the total product is shown. The single turnover results for each experiment were fit to a single exponential equation to yield the following kinetic parameters: WRN^949–1078 (■): A = 169 ± 5 nm, k_obs = 0.41 ± 0.04 min⁻¹; WRN^949–1078 (▴): A = 186 ± 5 nm and k_obs = 0.40 ± 0.04 min⁻¹.