Objective:To investigate the expression level of methyltransferase-like 3 (METTL3) in nasopharyngeal carcinoma cells CNE2 and CNE-2R, and to evaluate the effect of METTL3 on cell invasion, metastasis and radiosensitivity.Methods:Real-time reverse transcription PCR and Western blot were used to detect the expression levels of METTL3 in normal nasopharyngeal epithelial cells NP69 and nasopharyngeal carcinoma cells CNE2 and nasopharyngeal carcinoma radioresistant cells CNE-2R cells. METTL3 in CNE2 and CNE-2R cells was silenced by lentivirus-mediated RNA interference technology. The metastasis and invasion abilities of the cells were detected by the scratch assay and Transwell assay. Clonogenic assay and CCK-8 assay were employed to detect the proliferation capacity and viability of cells irradiated with different X-ray doses (0, 2, 4, 6 and 8 Gy). Apoptosis was detected by flow cytometry. Methylated RNA immunoprecipitation (Me-RIP) assay was used to detect the difference in m6A modification level of c-Jun in CNE2 and CNE-2R cells after METTL3 silencing. The transcriptional stability of c-Jun in cells after silencing METTL3 was detected by actinomycin D assay. A nude mouse xenograft model was constructed to detect the effect of METTL3 on the radiosensitivity of nasopharyngeal carcinoma in vivo. Results:Compared with NP69 cells, the expression levels of METTL3 mRNA and protein were significantly increased in CNE2 cells, and the expression level was even higher in CNE-2R cells (all P<0.01). Lentivirus-mediated RNA interference technology was used to construct a stable METTL3-silencing CNE2 and CNE-2R cell lines (both P<0.01). Scratch assay and Transwell assay showed that the metastasis and invasion abilities of CNE2 and CNE-2R cells were decreased significantly after METTL3 silencing (all P<0.05). Clonogenic assay showed that silencing METTL3 significantly reduced the number of colonies and survival fraction of CNE2 and CNE-2R cells after irradiation with different doses of X-rays (all P<0.05). CCK-8 assay showed that the proliferation ability of CNE2 and CNE-2R cells was significantly reduced by silencing METTL3 (all P<0.05). After different doses of irradiation, silencing METTL3 significantly reduced the survival fraction of CNE2 and CNE-2R cells (all P<0.05). The apoptotic rate after METTL3 silencing was higher than that in the control group at the irradiation dose of 0 and 8 Gy (all P<0.05). The Me-RIP assay showed that the m6A modification level of c-Jun in CNE2 and CNE-2R cells was significantly reduced after METTL3 silencing (both P<0.01), and the actinomycin D assay showed that transcriptional stability of c-Jun was reduced. Nude mouse xenograft experiment showed that silencing METTL3 inhibited xenograft proliferation and improved its radiosensitivity. Conclusion:METTL3 is highly expressed in nasopharyngeal carcinoma cells, and METTL3 mediates m6A modification of c-Jun to improve the transcriptional stability of c-Jun and promote the expression of c-Jun, thereby promoting the invasion and metastasis of nasopharyngeal carcinoma cells and reducing their radiosensitivity.

Objective:To investigate the expression level of methyltransferase-like 3 (METTL3) in nasopharyngeal carcinoma cells CNE2 and CNE-2R, and to evaluate the effect of METTL3 on cell invasion, metastasis and radiosensitivity.Methods:Real-time reverse transcription PCR and Western blot were used to detect the expression levels of METTL3 in normal nasopharyngeal epithelial cells NP69 and nasopharyngeal carcinoma cells CNE2 and nasopharyngeal carcinoma radioresistant cells CNE-2R cells. METTL3 in CNE2 and CNE-2R cells was silenced by lentivirus-mediated RNA interference technology. The metastasis and invasion abilities of the cells were detected by the scratch assay and Transwell assay. Clonogenic assay and CCK-8 assay were employed to detect the proliferation capacity and viability of cells irradiated with different X-ray doses (0, 2, 4, 6 and 8 Gy). Apoptosis was detected by flow cytometry. Methylated RNA immunoprecipitation (Me-RIP) assay was used to detect the difference in m6A modification level of c-Jun in CNE2 and CNE-2R cells after METTL3 silencing. The transcriptional stability of c-Jun in cells after silencing METTL3 was detected by actinomycin D assay. A nude mouse xenograft model was constructed to detect the effect of METTL3 on the radiosensitivity of nasopharyngeal carcinoma in vivo. Results:Compared with NP69 cells, the expression levels of METTL3 mRNA and protein were significantly increased in CNE2 cells, and the expression level was even higher in CNE-2R cells (all P<0.01). Lentivirus-mediated RNA interference technology was used to construct a stable METTL3-silencing CNE2 and CNE-2R cell lines (both P<0.01). Scratch assay and Transwell assay showed that the metastasis and invasion abilities of CNE2 and CNE-2R cells were decreased significantly after METTL3 silencing (all P<0.05). Clonogenic assay showed that silencing METTL3 significantly reduced the number of colonies and survival fraction of CNE2 and CNE-2R cells after irradiation with different doses of X-rays (all P<0.05). CCK-8 assay showed that the proliferation ability of CNE2 and CNE-2R cells was significantly reduced by silencing METTL3 (all P<0.05). After different doses of irradiation, silencing METTL3 significantly reduced the survival fraction of CNE2 and CNE-2R cells (all P<0.05). The apoptotic rate after METTL3 silencing was higher than that in the control group at the irradiation dose of 0 and 8 Gy (all P<0.05). The Me-RIP assay showed that the m6A modification level of c-Jun in CNE2 and CNE-2R cells was significantly reduced after METTL3 silencing (both P<0.01), and the actinomycin D assay showed that transcriptional stability of c-Jun was reduced. Nude mouse xenograft experiment showed that silencing METTL3 inhibited xenograft proliferation and improved its radiosensitivity. Conclusion:METTL3 is highly expressed in nasopharyngeal carcinoma cells, and METTL3 mediates m6A modification of c-Jun to improve the transcriptional stability of c-Jun and promote the expression of c-Jun, thereby promoting the invasion and metastasis of nasopharyngeal carcinoma cells and reducing their radiosensitivity.

Accurate prediction of the translation initiation site (TIS) is an important issue for prokaryotic genome annotation. However, it is still a challenge for the existing methods to predict the TIS in the genomes over a wide variety of GC content. Besides, the existing methods have not yet undergone a comprehensive evaluation, leaving prediction reliability as a largely open problem. A new algorithm MED-StartPlus, a tool that predicts TIS in prokaryotic genomes with a wide variety of GC content was presented. It makes several efforts to model the nucleotide composition bias, the regulatory motifs upstream of the TIS, the sequence patterns around the TIS, and the operon structure. Tests on hundreds of reliable data sets, with TISs confirmed by experiments or having annotated functions, show that the new method achieves a totally high accuracy of TIS prediction. Compared with existing TIS predictors, the method reports a totally higher performance, especially for genomes that are GC-rich or have complex initiation mechanisms. The potential application of the method to improve the TIS annotation deposited in the public database was also proposed.