Fig 2: GST-R1R2 was phosphorylated with Cyclin A/CDK2 where indicated as described in the Manuscript.B55a binding to GST-R1R2 was determined in the presence or absence of OA to prevent dephosphorylation. Proteins were resolved via SDS-PAGE and detected by western blotting using anti-B55a and GST antibodies. Two replicates of the experiment showed comparable results.

Fig 3: Loss of PPP2R2A/B55a overcomes Etoposide induced G2 checkpoint arrest.Asynchronously growing A2058 and A375 cells were transfected with either control or B55a siRNA. A Transfected cells were treated with 5 µM ICRF193 or 2 µM etoposide, and the G2 phase delay was quantified using time lapse imaging. The data are from three independent experiments. B Cell lysates were immunoblotted with B55a. a-Tubulin was used as a loading control. C siB55a transfected cells were treated with 2 µM etoposide, 500 nM BI2536 alone or in combination. G2 phase delay was quantified using time lapse imaging.

Fig 4: PP6C-AURKA-PLK1 dysregulation promotes chromosomal instability.A Histograms of the numbers of chromosomes in the isogenic A375 and A2058 pairs, counted in 50 mitotic chromosome spreads for each line. B The bars represent the cumulative dysregulation of PPP6C, AURKA, PLK1 and PPP2R2A/B55a as a percentage of total cases in TCGA pan cancer data set. BLCA, bladder cancer; BRCA, breast cancer; LIHC, liver hepatocellular carcinoma; LUAD, lung adenocarcinoma; CESC, cervical squamous cell carcinoma; COAD, colorectal adenocarcinoma; ESCA, oesophageal adenocarcinoma; HNSC, head and neck SCC; Liver, Liver hepatocellular carcinoma; LUSC, lung SCC; OV, ovarian cancer; STAD, stomach adenocarcinoma; SKCM, melanoma; UCS, Uterine carcinoma; SARC, sarcomas. C Correlation of the cumulative pathway score for PPP6C-AURKA-PLK1-PPP2R2A and CIN70 and HRD proliferation adjusted (prolif adj) scores for the indicated tumour types from TCGA.

Fig 5: MLH1 loss caused by DNMT3A/B upregulation is mediated through the PP2A-Rb-E2F pathway.a Immunoprecipitation performed with Capturem Protein A columns. Organoid lysates from WT mice were incubated with 1 µg of PPP2R1A antibody for 10 min. The antibody–lysate complex was applied to equilibrate Protein A spin columns. The eluted fraction was then subjected to SDS-PAGE to confirm the presence of PP2A B subunit antigen (52 kDa, detected by Cell Signaling #2290). Images are representative of one biological independent sample for each group. b Volcano plot for the comparison of RNA-seq data of Lgr5-EGFP-CreERT2; Ppp2r1aflox/flox intestinal organoids treated with and without DMBA and tamoxifen for 50 days. Differently expressed genes (fold change >2 and FDR < 0.05) are denoted in red or green. Plot is representative of three biological independent samples for each group. c Intersection of ppp2r1a interaction protein in a and differently expressed genes in b data (IP protein data are available in Supplementary Data 1 and RNA-seq data are available in GSE120241 with NIH/NCBI at GEO dataset). d The top 3 significant gene ontology categories from the 58 interacted proteins identified by GSEA (whole gene ontology category is listed in Supplementary Table 4). e Venn diagram showing overlap (gene numbers) among genes associated with regulation of TP53 activity, cell cycle, and RNA polymerase II transcription. The intersection contained four genes, including hdac2, ppp2cb, akt1, and rb1. Western blot analysis of f CT26 transfected with the indicated shRNAs, and treated with g vehicle control or 5-azacytidine (AZA, 1 µM for 1 days). Blots are representative of three biological independent samples for each group. h Human tissue array containing MSI and MSS colorectal tumours was assayed for p-Rb (n = 141, P = 0.0132) and p-HDAC2 (n = 138, P = 0.02) levels by immunohistochemistry. (Left) Representative pictures showing increased p-Rb and p-HDAC2 levels in MSI compared to MSS. Arrows indicate positive signals. Bar = 25 µm. (Right) Quantitative data are shown. P value was determined by two-sided Mann–Whitney U-test. Source data are provided as a Source data file.