Abstract:

OBJECTIVE: To investigate the role of ubiquitin protein ligase RING2 in cell cycle and expression of P53 in human bronchial epithelial cells exposed to benzo[a]pyrene. METHODS:The untreated 16HBE cellsgroups were used as negative control groups, the DMSO groups were used assolvent control groups, the MOCK groups were used as sequence control groups. 16HBE cells and 16HBE(siRNA-RING2) cells were exposed to BaP at different concentrations (1, 2, 4, 8, 16, 32 μmol/L) for 24 h, and were exposed to BaP at 16 μmol/L for different time points (1, 2, 4, 8, 12, 24 h). Flow cytometry was used to evaluate the cell cycle. The levels of P53 protein were detected by Western-blot. RESULTS:After BaP treatment, compared with the negative control groups, at each concentration and each time point the proportion of S phase of 16 HBE cells were significantly increased (P<0.01). However at each concentration and each time point 16HBE (siRNA-RING2) cells groups the proportion of S phase cells were significantly decreased (P<0.01). Covariance analysis shows grouping factors (with or without RNAi) and all concentrations had impact on the proportion of S phase, P values were both less than 0.01. The estimated mean of the proportion of S phase in 16HBE (siRNA-RING2) cell group (17.09%) was significantly lower than that of 16HBE cell group (31.55%). Grouping factors (with or without RNAi) and the exposure time all have impacted on theproportion of S phase, P values were both less than 0.01. The estimated mean of the proportion of S phase in 16HBE (siRNA-RING2) cell group (13.07%) was significantly lower than that of 16HBE cell group (28.04%) (P<0.05). After BaP treatment, compared with the negative control group, at each concentration and each time point P53 protein levels at 16 HBE cell groups were significantly increased (P<0.05). However, at each concentration and each time point 16HBE (siRNA-RING2) cell groups (except 16 μmol/L BaP treated 8 h) the levels of P53 protein were significantly decreased (P<0.05). Covariance analysis shows grouping factors (with or without RNAi) and all concentration showed impact on the level of P53 protein, P values were 0.026 and 0.028, respectively. The estimate mean of the levels of P53 protein in 16HBE (siRNA-RING2) cell group (0.989) was significantly lower than that of 16HBE cell group (1.375) (P<0.05). Grouping factors (with or without RNAi) and the exposure time both impacted on the level of P53 protein, P values were 0.007 and 0.035, respectively. The estimate mean of the levels of P53 protein in 16HBE (siRNA-RING2) cell group (0.857) was significantly lower than that of 16HBE cell group (1.541) (P<0.05). CONCLUSION:The histone ubiquitination modifications in which RING2 was involved may regulate DNA repair by affecting the expression of P53 and cell cycle S phase changes.

Key words: benonzo[a]pyrene, human bronchial epithelial cell, ubiquitin protein ligase RING2, cell cycle, P53