[Effects of hnRNP B1 on DNA-PK activity, cell cycle and apoptosis in human lung adenocarcinoma cell line A549].

OBJECTIVE: To explore the effects of hnRNP B1 on DNA-PK activity, cell cycle and apoptosis in human lung adenocarcinoma cell line A549. METHODS: hnRNP B1 siRNA expression vectors (recombinant plasmid A and D) were constructed according to the different targeting sequences of hnRNP B1 gene. The recombinant eukaryotic expression plasmid A and D were identified by PCR and sequence analysis, and then were transfered into A549 cells respectively by Lipofectamine 2000, with or without preincubation of 10 micromol/L NU7026 (a specific inhibitor of DNA-PK) for 1 h. The expression of hnRNP B1 was measured by Western blot. DNA-PK activity was detected with SigmaTECT DNA-Dependent Protein Kinase Assay System. Cell cycle and apoptosis were analyzed by flow cytometry. RESULTS: The expression vectors were successfully constructed. The expression of hnRNP B1 protein were reduced in the cells transfected with hnRNP B1 siRNA. The activity of DNA-PK in A549 cells transfected by hnRNP B1 siRNA was significantly higher than that of untransfected cells (P < 0.05). After the transfection of hnRNP B1 siRNA, the cells in G1 phase increased but those in S phase decreased, while the rate of apoptosis increased. With the treatment of NU7026, the number of G1 cells decreased,that of S cells increased and cell apoptosis were significantly inhibited. DNA-PK activity was significantly positive correlation with the rate of apoptosis. CONCLUSION: hnRNP B1 could affect the stability of cell genome and regulate the cell cycle and apoptosis by inhibiting DNA-PK activity.