FIGURE 1.

Full-length WRN^1–1432 stimulates hpol η^1–437 core polymerase domain. A, an overview of the hpol η and WRN proteins showing domains with either structural or catalytic properties for each enzyme. PIR, PCNA interacting region; RIR, Rev1-interacting region; UBZ, ubiquitin binding zinc-finger domain; HRDC, Helicase and RNaseD C-terminal; PIP, PCNA interacting peptide; NLS, nuclear localization signal. B, hpol η^1–437 (2 nm) polymerization was allowed to proceed on a DNA substrate (200 nm) possessing a 5-nucleotide ssDNA overhang (13/18-mer) in either the presence (●) or absence (○) of full-length WRN (100 nm). C, DNA synthesis by hpol η^1–437 (2 nm) was monitored over time using a 13/18-mer primer-template DNA substrate (200 nm) in the absence of WRN and in the presence of full-length WRN^1–1432 (100 nm). Total product formation (i.e. all of the product bands from panel B) is shown. The experiments were performed in triplicate and the mean ± S.D. is shown. The single-turnover results for each experiment were fit to a single-exponential equation to yield the following kinetic parameters: No WRN (●): A = 178 ± 6 nm, k_obs = 0.26 ± 0.03 min⁻¹; WRN^1–1432 (■): A = 192 ± 2 nm, k_obs = 0.98 ± 0.04 min⁻¹.