The target protein was found to be enriched in the 100 mM imidazole Tanespimycin molecular weight eluent. All samples were analyzed by 12% SDS-PAGE. The p16INK4a fusion protein was further verified by Western blotting using a specific anti-p16INK4a antibody (Figure 4b). Figure 4 Purification, verification, and transduction of exogenous p16INK4a fusion protein. a. Successful
expression and purification of the p16INK4a fusion protein was confirmed by 12% SDS-PAGE analysis. The bacterial sample before IPTG induction showed almost no protein expression (lane 1). After IPTG induction and centrifugation, p16INK4a fusion protein was abundant in the clear supernatant (lane 3) (indicated by the arrow) and absent from the bacterial precipitate (lane 2). The supernatant was loaded onto a Ni2+-affinity chromatography column, which binds the His-p16INK4a fusion protein. Nonspecifically bound proteins were removed with washing buffer; the flow-through liquid can be seen in lane 4. Elution buffer with different concentrations of imidazole was used to elute the p16INK4a fusion protein: 20 mM (lane 5), 50 mM nt (lane 6), 100 mM (lane 7) and 200 mM (lane 
were. The fractions were assessed by SDS-PAGE and the sample corresponding to the 100 mM imidazole eluent (lane 7) was found to contain p16INK4a fusion protein of high purity (arrow). b. The purified protein was Dabrafenib research buy verified by Western-blot
analysis using the specific p16INK4a antibody. c. Immunocytochemical assay to assess transduction efficiency. All nuclei of A549 cells stained with Hoechst fluorescent and the exogenous p16INK4a protein was detected in about 50% of cells, as shown by the FITC signal. As shown in the figure, the transduction efficiency
was about 50%. Purified p16INK4a fusion protein was transduced into A549 cells and transduction efficiency was examined by fluorescence immunocytochemistry. As shown in Figure 4c, all A549 cell nuclei were positive for Hoechst fluorescence and about 50% were positive for FITC, indicating that these cells had been successfully transduced with p16INK4a. Growth suppression of A549 cells following p16INK4a induction To evaluate the effect of p16INK4a on cell growth, the growth curves of A549 cells transduced with the protein were compared with those of control cells (A549 cells incubated with Lipofectamine 2000). Cells transduced with p16INK4a the day before the ADAM7 start of the experiment were counted at 12-h intervals. Figure 5a shows that, 36 h after cell subculture, p16INK4a began to induce growth retardation. At 72 h, p16INK4a had significantly suppressed proliferation compared with the control (Figure 5a, b). Furthermore, cell cycle changes, as analyzed by flow cytometry (Figure 5c), showed that the presence of exogenous p16INK4a resulted in a marked retardation of the G1→S transition of A549 cells 48 h after transduction. Figure 5 Cell growth inhibition and cell cycle redistribution effects of p16INK4a in A549 cells.