Figure 4.

The polymerase stimulation activity of Mrc1 is abrogated in the DNA-binding defective or phospho-mimetic mutants. (A) Primer extension assays were conducted as described in Fig. 1E in the presence of increasing amount of Mrc1 WT or mutant proteins (0–100 nM). 100 nM Mrc1 proteins alone (WT, mrc1-3KA, mrc1-3KE or mrc1-3D) were examined in parallel to confirm that they do not contain any contaminating DNA polymerase activity. (B) Quantification of (A) from three independent repeats. The fully extended primers were quantified by Typhoon ImageQuant. The activity of DNA polymerase alone was normalized to 100%. Mean ± SD are shown from three independent experiments. Statistical significance was measured using Student's t-test. **P < 0.01; *P < 0.05; n.s., not significant.