Figure 1.

DDX41 binds to the 3′UTR of the p21 mRNA, regulating its expression. A, Western blot analyses for the presence of the indicated proteins in immunoprecipitates of BrU-labeled p21 mRNAs that, in addition to the ORF, contained either the 5′UTR or the 3′UTR. Prior to immunoprecipitation (IP), the p21 mRNAs were incubated for 2 h with cytoplasmic extracts of untreated HCT116 wild-type cells. Cytoplasmic extract that was not subjected to RNA immunoprecipitation served as a control (Input). B–D, Western blot analyses for the status of the indicated proteins in HCT116 wild-type cells that were either left untransfected or transfected with the indicated siRNAs. Samples were probed 8 h after γIR (B and C) or on the indicated days following exposure to etoposide (D). Contr., control; Casp2, caspase-2. In A–D, the blots shown are representative results of two (A), three (B and D), and four (C) independent experiments. For densitometric and statistical analyses of the p21 and p53 blots shown in B–D, refer to supplemental Figs. S1–S3.