Fig. 3.

METTL14 inhibition suppresses repair of UVB-induced DNA damage. (A) Immunoblot analysis confirming METTL14 knockdown, dot blot assay of the m⁶A levels (Left), and quantification of the m⁶A/A ratios in polyadenylated RNA by UHPLC-MS/MS (Right, n = 3) in HaCaT cells stably infected with shRNA targeting negative control (shNC) or METTL14 (shM14-1, shM14-2). (B) Slot blot analysis of UVB-induced CPDs in control or METTL14-knockdown HaCaT at different time points post-UVB irradiation (20 mJ/cm²). (C) Quantification of B (mean ± SE, n = 3). (D) Immunoblot analysis confirming overexpression of WT METTL14 or R298P mutant METTL14, dot blot assay of the m⁶A levels (Left), and quantification of the m⁶A/A ratios in polyadenylated RNA by LC-MS/MS (Right, n = 3) in HaCaT cells transfected with empty vector (EV), WT, or R298P mutant METTL14. (E) Same as B except that cells in D were used. (F) Quantification of E (mean ± SE, n = 3). Methylene blue (MB) was used as an equal loading control for total RNA (A and D) and DNA (B and E). *P < 0.05; **P < 0.01; ***P < 0.001; ns, not significant; Student’s t test, significant differences from shNC (C) or EV (F) groups.