Phosphorylation of MCM4 at sites inactivating DNA helicase activity of the MCM4-MCM6-MCM7 complex during Epstein-Barr virus productive replication. J Virol. 2006;80:10064-10072. [PMID: 17005684 DOI: 10.1128/JVI.00678-06J]

Effects of RNA interference-mediated MCM7 knockdown on biological behavior of human liver cancer SMMC-7721 cells

AIM: To investigate the effects of mini-chromosome maintenance protein7 (MCM7) gene silencing on the proliferation and apoptosis of human liver cancer SMMC-7721 cells and the possible mechanisms involved.

METHODS: Four vectors carrying shRNAs targeting the MCM7 gene (MCM7-shRNA expression vector) were constructed and were selected for effective targets. SMMC-7721 cells were divided into three groups: an experimental group, a normal control group and a negative control group. The experimental group was transfected with the recombinant lentivirirus vector (LV-shRNA-MCM7), the negative control was transfected with an control lentiviral vector (LV-shRNA-NC), and the normal control received no treatment. The mRNA and protein levels of MCM7 were analyzed by RT-PCR, quantitative real-time PCR (qPCR), and Western blot. Cell proliferation was detected by MTT assay, and cell colony formation was detected by Giemsa staining. Cell cycle progression and apoptosis were observed by flow cytometry (FCM).

RESULTS: MCM7-shRNA expression vectors were successfully constructed and verified by DNA sequencing. After transfecting SMMC-7721 cells with various vectors, cell fluorescence was observed in > 90% of cells. MCM7 mRNA and protein expression in the four MCM7-shRNA groups was down-regulated by > 50% compared with the negative control group and normal control group. The LV-shRNA-MCM7 vector had the highest efficiency and was used in subsequent experiments. MTT results showed that cell proliferation in the experimental group at 24, 48, 72 and 96 h after transfection was significantly lower than that in the negative control group and normal control group (P < 0.05 for all). Giemsa staining results showed that the colony formation rate was significantly lower in the experimental group than in the two control groups (6.00% ± 0.50% vs 14.10% ± 0.36%, 13.73% ± 0.17%, P < 0.05 for both). FCM analysis showed that the percentage of cells in G₁ phase increased in cells transfected with the MCM7-shRNA (P < 0.05 for both). The apoptosis rate was significantly higher in the experimental group than in the negative control group and blank control group (22.27% ± 1.22% vs 0.05% ± 0.07%, 0.03% ± 0.06%, P < 0.05 for both).

CONCLUSION: RNAi-induced MCM7 down-regulation could inhibit cell growth, suppress cell colony formation, block the cell cycle at G₁ phase, and induce cell apoptosis in SMMC-7721 cells.