Figure 6: CHIP-mediated degradation of XRCC1 is regulated by HSP90.
From: HSP90 regulates DNA repair via the interaction between XRCC1 and DNA polymerase β

Overexpression of the E3 ligase CHIP enhances the 17-AAG-mediated degradation of XRCC1 in (a) LN428/MPG/Polβ-KD/Flag-Polβ(TM) cells and (b) T98G/MPG/Polβ-KD/Flag-Polβ(TM) cells: immunoblot of WCLs from stable LN428/MPG/Polβ-KD cell lines (a) or T98G/MPG/Polβ-KD/Flag-Polβ(TM) cell lines (b) expressing Flag-Polβ(WT), Flag-Polβ(TM) or EGFP after exposure to 17-AAG at the concentrations indicated and after overexpression of CHIP, as indicated. The immunoblot images depict the levels of XRCC1, CHIP and PCNA, before and after treatment with 17-AAG, showing the stability of XRCC1 in the cells expressing Flag-Polβ(WT) and the rapid degradation of XRCC1 in the cells expressing Flag-Polβ(TM) or EGFP. Representative immunoblot images are shown. (c) CHIP knockdown efficiently prevents 17-AAG-mediated degradation of XRCC1 in LN428 cells: immunoblot of WCLs from stable LN428 cells expressing CHIP-specific shRNA (shCHIP.2 or shCHIP.1) or GFP (control) after exposure to 17-AAG at the concentration indicated. The immunoblot image shows the level of XRCC1, CHIP and PCNA (loading control), before and after treatment with 17-AAG.