Fig 1: TFIP11 promotes fork reversal.A Electron micrograph illustrating a representative replication fork or reversed fork. P denotes parental duplex, D indicates daughter duplexes, and R indicates the regressed arm. B Frequency of reversed forks. Data presented as mean ± SD from three independent experiments, with the total number of analyzed replication intermediates across three replicates shown in brackets. P values were derived from a one-way ANOVA with Tukey’s multiple comparisons test. C Top: schematic of the native BrdU assay. Bottom: Model for the native BrdU assay. Black and green lines represent template and nascent DNA strands, respectively. D, E HeLa cells were labeled with 10 μM BrdU for 15 min before treatment with 4 mM HU for 3 h. Cells were then fixed and stained with antibody against BrdU without DNA denaturation. Representative BrdU foci shown in (D). Scale bar, 10 μm. Quantification of BrdU foci (E). Data represent mean ± SD from three independent experiments. From left, n = 480, 538, 534, 775, 413, 467 cells. P values were derived from a one-way ANOVA with Tukey’s multiple comparisons test. F Top: schematic representation of the DNA fiber assay. Bottom: representative fiber images. G Dot plot of CldU/IdU ratios for individual replication forks. The results shown represent the mean ± SD of three independent experiments. From left, n = 116, 115, 115, 119, 121 cells. P values were derived from a one-way ANOVA with Tukey’s multiple comparisons test. H Fork speed determined by DNA fiber assay. The results shown represent the mean ± SD of three independent experiments. P values were derived from a one-way ANOVA with Tukey’s multiple comparisons test. I Top: schematic representation of the DNA fiber assay. HeLa cells were sequentially labeled with IdU and CldU for 15 min and then challenged with 4 mM HU for 5 h. Bottom: representative fiber images. J Dot plot of CldU/IdU ratios for individual replication forks. The results shown represent the mean ± SD of three independent experiments. From left, n = 113, 107, 118, 108, 105, 120 fibers. P values were derived from a one-way ANOVA with Tukey’s multiple comparisons test. K Knockdown of TFIP11 and BRCA1/2. Asterisk indicates a non-specific band. Source data are provided as a Source Data file.