Fig 1: BIRC5 modulates the protein stability of ATG7 and the expression of ATG12–ATG5 conjugate in cancer cells. (A) Cells were transfected with the scramble siRNA, BIRC5 siRNA, empty plasmid DNA, or the BIRC5 expressing pCMV6-XL4-BIRC5 for the indicated durations. Expression of different proteins was determined by the western blot analysis. ACTA1 was used as an internal control. (B) Cells were transfected with the empty plasmid DNA, the BIRC5 expressing pCMV6-XL4-BIRC5, scramble siRNA, or BIRC5 siRNA for 48–72 h. The relative amount of ATG7 mRNA transcripts present in cells was analyzed by qPCR. A “N.S.” denotes no statistical significance difference between the testing groups. (C) MDA-MB-231 and A549 cells were transfected with either the empty plasmid DNA (-ve control) or BIRC5 expressing pCMV6-XL4-BIRC5 (O/E BIRC5) for 48 h. Cycloheximide was added to the cells to inhibit de novo protein synthesis. Cells were then harvested at the time points indicated and expression of ATG7 was analyzed by western blotting. Experiments were repeated three times and representative blots were shown. Signals in the blots (of all repeats) were quantitated and a graph was generated to compare the degradation rates. A statistically significant difference in the mean of the relative band intensity (of all repeats) of ATG7 in cells transfected with the empty plasmid DNA vs. the BIRC5-expressing plasmid DNA at the same time point is denoted by “*” (p < 0.05), “**” (p < 0.01), or “***” (p < 0.001).