Journal: International Journal of Molecular Sciences
Article Title: DEAD/H Box 5 (DDX5) Augments E2F1-Induced Cell Death Independent of the Tumor Suppressor p53
doi: 10.3390/ijms252413251
Figure Lengend Snippet: DDX5 enhances E2F1 induction of endogenous target gene expression and cell death in normal cells. ( A ) DDX5 enhances over-expressed E2F1 activity in human normal fibroblasts (HFF). HFFs were transfected with the ARF or TAp73 reporter plasmid and E2F1 expression plasmid with increasing amounts (0, 125, 250, 500 ng) of DDX5 expression vector. Fold activations by E2F1 are shown. ***: p < 0.01. ( B ) DDX5 enhances endogenous deregulated E2F activity in normal cells. HFFs were transfected with the ARF reporter plasmid with E1a and DDX5 expression vectors. ***: p < 0.01. ( C ) Enhancement by DDX5 is through deregulated E2F1 activity. HFFs were transfected with a reporter plasmid possessing 3 tandem repeats of the ARF promoter E2F-responsive element (EREA (WT)), or its E2F binding site mutant (EREA (mt)), upstream of an SV40 core promoter (pGL3-Promoter), along with E2F1 and DDX5 expression vectors. pGL3-Promoter was used as a negative control. Fold induction by E2F1 is shown. ***: p < 0.01. ( D ) Enhancement of over-expressed E2F1 activity by DDX5 does not depend on helicase activity. Effects of helicase mutant DDX5(K144R) on E2F1 activation of the ARF (left panels) and TAp73 (right panels) promoters were examined at 500 ng of expression vector in as in ( A ). **: p < 0.05, ***: p < 0.01. ( E ) DDX5 enhances E2F1 induction of endogenous gene expression. HFFs were infected with Ad-FLAG-E2F1 (multiplicity of infection (MOI): 20) along with or without Ad-DDX5 or Ad-DDX5(K144R) (MOI: 50). The cells were further cultured for 48 h in the absence of serum and harvested. mRNA levels of ARF, BIM, and Aspp1 genes were examined by qRT-PCR. **: p < 0.05, ***: p < 0.01. ( F ) DDX5 enhances E2F1 induction of cell death. HFFs were infected with Ad-FLAG-E2F1 (MOI: 20) along with or without Ad-DDX5 or Ad-DDX5(K144R) (MOI: 50). The cells were cultured for 3 days and harvested. The percentage of dead cells was determined by FACS analysis as those with subG1 DNA content. ***: p < 0.01. ( G ) Expression of E2F1 and DDX5 protein levels were determined by western blot analysis under the same condition as in ( E ). β -actin was used as an internal control. ( H ) Expression levels of FLAG-E2F1 and DDX5 together with ARF, p53, and TAp73 were examined by western blot analysis under the same conditions as above. β -actin was used as an internal control. ***: p < 0.01. ( I ) DDX5 enhances endogenous deregulated E2F activity. HFFs were infected with Ad-12SE1a(∆2–11) (MOI: 200) along with or without Ad-DDX5 (MOI: 50). The cells were further cultured for 48 h in the absence of serum and harvested. mRNA levels of ARF, BIM, and Aspp1 genes were examined by qRT-PCR. **: p < 0.05, ***: p < 0.01. ( J ) Expression levels of E1a and DDX5 together with E2F1 were examined by western blot analysis.
Article Snippet: The cells were infected with Ad-FLAG-Con or Ad-FLAG-E2F1 (MOI 20), and cultured for 48 h. For the endogenous E2F1 experiment, the cells infected with Ad-12SE1a(∆2–11) or Ad-Con (MOI 200), and cultured for 48 h. The cells were fixed and stained by mouse anti-E2F1 antibody (sc-251, Santa Cruz Biotechnology, 1:250) or rabbit anti-DDX5 antibody (ab126730, Abcam, Cambridge, UK, 1:250) and, as second antibodies, Goat anti-Mouse IgG (H + L) Cross-Absorbed Alexa Fluor 546 (A11018, Invitrogen, 1:1000) or Goat anti-Rabbit IgG H&L Alexa Fluor 488 (ab150077, abcam, 1:1000).
Techniques: Targeted Gene Expression, Activity Assay, Transfection, Plasmid Preparation, Expressing, Binding Assay, Mutagenesis, Negative Control, Activation Assay, Gene Expression, Infection, Cell Culture, Quantitative RT-PCR, Western Blot, Control