Figure 6.

HITTERS regulates ER stress related DDR. A) qPCR and B) Western blot confirmed that knocking‐down HITTERS did not significantly change the mRNA and protein expression of HERPUD1. For qPCR, cells were transfected with siRNA for 48 h. Student t‐test was used for qPCR. C,D) Knocking‐down HITTERS did not significantly change the mRNA level of important UPR regulator in both C) SCC25 and D) CAL27 cells. Cells were transfected with siRNA for 48 h and then treated with TM (10 µg mL⁻¹) for 6 h. E) GSEA results for RNA‐sequencing profiles. SCC25 cells were transfected with HITTERS siRNA or negative control siRNA for 48 h and then treated with TM (10 µg mL⁻¹) for 12 h. F,G) 2',7'‐dichlorofluorescein staining and TUNEL assay indicated TM (10 µg mL⁻¹, 24 h) treatment promoted F) ROS production and G) DNA breaks. Student t‐test was used. H) Induction of ER stress by TM (10 µg mL⁻¹) significantly promoted the level of DNA damage marker γ‐H2AX and suppressed DNA repair proteins in a time‐dependent manner. I) Knocking‐down HITTERS significantly suppressed DNA repair protein and promoted DNA damage marker expression; J) whereas overexpressing HITTERS obtained the opposite effect. Cells were transfected with siRNA or plasmid for 48 h and then treated with TM (10 µg mL⁻¹) for 24 h. Note: ns, no significance; ***, P < 0.001.