FIG. 1.

Substrate specificity of pol μ. (A) A single-nucleotide-gapped DNA substrate with template C was present (5 nM) in all reaction mixtures (diagrammed in panel C; “1 nt gap”). dGTP or rGTP (100 μM) was included as indicated. Wild-type pol μ (μ; 0.5 nM), pol β (β; 0.5 nM), or mutant pol μ (mut; 50 nM) was added as noted. Reaction time was 1 min. (B) pol μ (5 nM), rNTP substrate (1 mM), and 1-nt-gapped DNA substrate (5 nM) (as in panel A) with either A, C, G, or T as the templating base were included as indicated. Reaction time was 1 min. (C) The specific activity of pol μ (femtomoles of product per minute per milligram of pol μ) was determined with 5 nM nucleic acid substrate and a 25 μM concentration of each of the four dNTPs or rNTPs. Concentrations of pol μ and reaction times were varied such that reactions were in the linear range. Dotted lines indicate RNA strands substituted for DNA in the standard 1-nt-gappedsubstrate. The means of three replicate experiments performed in the linear range are shown. The standard deviation was less than 15% of the mean for all substrates tested.