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. 2023 Dec 16;9:459. doi: 10.1038/s41420-023-01754-x

Fig. 3. Active-site engagement of SR-4835 promotes CDK12 binding to DDB1.

Fig. 3

A Immunoblot depicting cyclin K levels in A375 cells depleted for DDB1 using shRNA constructs and treated with SR-4835 (1 µM) for 2 h. shRNA efficiency was assessed by immunoblotting with the anti-DDB1 antibody, or by qPCR. B HEK293 cells were transfected with Myc-tagged CDK12, HA-tagged cyclin K and Flag-tagged DDB1, and treated for indicated times with SR-4835 (1 µM) or THZ531 (1 µM). Immunoprecipitated Myc-CDK12 was assayed for co-IP with DDB1 and cyclin K. C A375 cells were treated with THZ531 at indicated concentrations for 45 min before SR-4835 (1 µM) treatment for another 2 h. Cyclin K levels were assessed by immunoblot. D Docking pose of SR-4835 and CR8 in the active site of CDK12 (PDB: 6TD3) with key residues highlighted. E Docking pose of SR-4835 in the active site of CDK12 in association with DDB1 and cyclin K (PDB: 6TD3). A–C Representative data of n = 3. Data are represented as mean ± SD of independent experiments (n = 3) and significance was determined using unpaired two-tailed Student’s t-tests (A). P-values signification: **P < 0.01.