(A) Tet1, Tet2, and Tet3 mRNA expression levels in mouse fibroblasts 48 hr after RNAi depletion of Tet1, Tet2, or Tet3. **p<0.01, two-tailed Student’s t-test. (B) Dot blot of R-loops, 5-hydroxymethylcytosine (5hmC), and 5-methylcytosine (5mC) in Tet1, Tet2, and Tet3 single KD and in Tet1/2/3 triple KD mouse fibroblast extracts. dsDNA was detected after stripping and reprobing of the same membranes. Data are from three independent experiments. Quantification of the 5hmC, 5mC (C), and R-loops (D) dot blots shown in (B). *p<0.05, two-tailed Student’s t-test. ND, not detected. (E) DNA:RNA immunoprecipitations (DRIPs) performed in Tet1/2/3 triple KD mouse fibroblasts to assess the R-loop levels formed in the indicated genes. R-loop levels were normalized to the corresponding RNase H-treated sample. *p<0.05, **p<0.01, ***p<0.001, two-tailed Student’s t-test. (F) Transcription levels of the genes presented in (E) in control and Tet1/2/3 triple KD mouse fibroblasts. All graphs show the mean and SD from a minimum of three independent experiments.