Figure 8. Natamycin inhibits BER enzymes pol β and LIG I.

A. The inhibitory effect of natamycin on LIG I activity was examined with the substrate containing a nick. Lane 1 represents the substrate only. Lanes 2 and 3 indicates the reaction mixture with 5 nM LIG I in the absence and presence of DMSO. Lanes 4-7 correspond to the reaction mixture with 5 nM LIG I in the presence of increasing concentrations of natamycin. The substrate was ³²P-labeled at the 5’-end of the upstream strand and is illustrated above the gel. The experiments were repeated at least three times. Representative gel is illustrated. Quantification of the results is shown below the gel. Two-way ANOVA with Tukey’s multiple comparison posttests was used to determine statistically significant differences. * signifies p<0.05 compared to the control reaction with LIG I and DMSO. It should be noted that upper band is the smearing of the ligated products in the course of gel electrophoresis. B. The inhibitory effect of natamycin on pol β DNA synthesis was determined with the substrate containing a 1-nt gap as described in the “Materials and Methods”. Lane 1 represents the substrate only. Lanes 2 and 3 indicates the reaction mixture with 5 nM pol β in the absence and presence of DMSO. Lanes 4-7 correspond to the reaction mixture with 5 nM pol β in the presence of increasing concentrations of natamycin. The substrate was ³²P-labeled at the 5’-end of the upstream strand and is illustrated above the gel. The experiments were repeated at least three times. Quantification of the results are shown below the gel. Two-way ANOVA with Tukey’s multiple comparison posttests was used to determine statistical significance. * signifies p< 0.05 compared to the control reaction with pol β and DMSO.