Background and purpose: DNMT3B has nearly 40 known splice variants expressed in a tissueand disease-specific manner

but the roles of these splice variants in the cell are still unclear. The aim of this study was to investigate the effects of overexpression of DNA methyltransferase 3B4 (DNMT3B4) gene on proliferation of human embryo kidney 293A cells. Methods: 293A cells were transfected with plasmid pCMV-DNMT3B4 or pCMV-2B and then treated with G418 to get the stable cell line. The stable cell lines were determined for proliferation level by MTT method

and for cell cycle distribution by flow cytometry. The expression of p21 was detected by real-time PCR and Western blot. The methylation status of p21 gene promoter was detected by methylation-specific PCR (MS-PCR). Results: The absorbance value in DNMT3B4-1 and DNMT3B4-2 clone were (58.92±3.47)% and (68.82±5.64)% as compared to 293A-vector cells using MTT method. DNMT3B4 overexpression significantly decreased cell proliferation (P0.05). S phase fraction of 293A-vector cells was (40.44±0.91)%. While in DNMT3B4-1 and DNMT3B4-2 clone cells

the S phase fraction was (35.88±2.00)% and (37.00±1.79)% respectively. Overexpression of DNMT3B4 could significantly decrease S phase fraction (P0.05). The expression of p21 in DNMT3B4 overexpressed cells was increased

but the methylation status of p21 gene promoter was unchanged.Conclusion: Overexpression of DNMT3B4 can inhibit 293A cell proliferation and can facilitate p21 expression.