Fig. 4.

Clustering reveals a MAPK mediated early and CDK mediated late response to BRAF inhibition. A, Selected phosphoproteomics clusters show an early and late response of phosphosites in which phosphorylation decreases upon BRAF inhibition within 2–6 h (left panel) and after 24–48 h (middle panel). Enrichment analysis (right panel) indicates that the early response cluster is enriched for substrates of kinases located downstream of BRAF in the MAPK pathway, whereas the late response cluster is enriched for substrates of cyclin-dependent kinases. B, Selected transcriptomics clusters show a similar early (left panel) and late (middle panel) response. Enrichment analysis (right panel) reveals that the early response cluster is enriched for target genes of transcription factors that are downstream of the MAPK pathway, and the late response cluster is enriched for targets of the E2F-transcription factor. C, Deactivation of MYC is a consequence of MAPK pathway deactivation and corroborates the early-response TF-target gene enrichment analysis. D, Downregulation of RB1 at phosphosite T821 inhibits E2F1 activity and induces cell cycle arrest at late timepoints in BRAFi treated cells.