Extended Data Fig. 8: The CIP2A-TOPBP1 interaction does not impact ATR activation but promotes viability of MDA-MB-436 cells.
a, Immunoblots assessing CHK1 S345 phosphorylation in DLD1 cells transduced with either an empty virus (EV) that expresses the DD domain alone or a virus expressing DD-tagged B6L following induction with 1 μM AS1. Cells were treated with hydroxyurea (HU) at the indicated doses for 24 h before harvesting. Representative of two independent transductions. b, Immunoblots assessing CHK1 S345 and RPA2 pS33 phosphorylation in whole-cell lysates of RPE1-hTERT p53-/- Cas9 parental (WT) or independent CIP2A-/- clones. Cells were treated with camptothecin (CPT; 1 μM) for the indicated times prior to harvesting. Representative of two independent immunoblots. c, Anti-FLAG immunoblots of whole-cell extracts from MDA-MB-436 cells treated with Aqua-Shield-1 (AS1) for 72 h. KAP1 is used as loading control. Representative of three independent immunoblots. d, Proliferation curves for MDA-MB-436 cells upon B6L stabilization by AS1 treatment (1 μM). Cells were transduced with an empty virus (EV) as control. Representative of three proliferation assays, analyzed with a Mann-Whitney test; U value (normal approximation)= -5.612486, -5.163978. e, Quantitation of independent proliferation experiments described in (d). Data presented as the mean values at endpoint ± S.D. n = 3 proliferation assays; analyzed with a t-test, assuming data is normally distributed, ∗∗p = 0.0038. f, Quantitation of micronuclei (MNi)-positive cells in MDA-MB-436 cells transduced with an either empty virus (EV) or B6L-expressing virus following addition of AS1. Data presented as the mean ± S.D. n = 3 independent MNi counts; analyzed with two-way ANOVA with repeated measures and Šídák’s multiple comparisons testing. ∗∗∗p = 0.00015. Statistical analyses and full blots are found in Source Data ED Fig. 8.
