Lack of the FBXW7-WD40 domain results in the accumulation of FBXW7 substrates NICD and c-MYC. (A) Heterozygous or homozygous indel mutations were induced in FBXW7 at the protein amino acid position 396 in the CLL cell line HG-3 using CRISPR-Cas9. (B) FBXW7, Cyclin E, p100/p52, c-MYC, and NICD protein levels were analyzed in FBXW7-mutated HG-3 cell lines via western blot (representative of 3 blots). (C) c-MYC promoter activity (n = 3) and (D) transcription factor activity of NOTCH1 (n = 3) was quantified in HG-3 wt and HG-3 clones with FBXW7 truncation using luciferase reporter plasmids with the respective transcription factor binding motifs. Overexpression of the NOTCH1 coactivator RBP was used as positive control. Statistical significance was assessed via 1-way analysis of variance followed by Bonferroni’s posttest (****P < .0001; ***P < .001; *P < .05).