Figure 6. Parkin deficiency attenuates Polη recruitment to damage sites and leads to higher mutation frequency.

(A–B) Parkin deficiency was detrimental for recruitment of Polη to UV-induced damage sites. WT or Parkin−/− cells transfected with GFP-Polη were irradiated with 15 J/m² UV and further incubated for 8 h. Then cells were fixed and the proportion of cells with GFP-Polη foci was determined. (A) Representative images of Polη foci formation in WT and Parkin−/− cells. (B) Quantification of the percentage of cells with more than 30 GFP-Polη foci. Error bars represent SD. t-test, n = 3. (C–D) Parkin deficiency led to higher mutation frequency. (C) 293T cells were transfected with siParkin or siNC. 72 h later, the cells were harvested and the levels of Parkin were detected by western blot. β-actin: loading control. (D) The Parkin-depleted 293T cells were transfected with pSP189 plasmid which was pre-irradiated with 360 J/m² UV, and replicated for 72 h. The pSP189 plasmid was then extracted and DpnI digested followed by transformation into MBM7070 bacteria strain for mutation frequency analysis. Error bars represent SD. t-test, n = 3. (E) Model for Parkin's function in regulating TLS.