Abstract: OBJECTIVE: To construct eukaryotic expression vectors with FLAG epitope that can highly express human cyclin D1 and cyclin B1 genes，then transiently transfect into human cervical cancer HeLa cell line. METHODS：cDNA of cyclin D1 and cyclin B1 genes from total RNA isolated from HeLa cells was amplified by RT-PCR. After sequencing，the open reading frame (ORF) of cyclin D1 and cyclin B1 cDNA was cloned into eukatyotic expression vector p3XFLAG-CMVTM-14 to form the recombinant plasmid named as p3XFLAG-cyclin D1 and p3XFLAG-cyclin B1. Then eukatyotic expression vectors were transfected into HeLa cells by Lipofectamine 2000. Expressions of human cyclin D1 and cyclin B1 in HeLa cells were measured by Western blot. RESULTS：The result of restriction enzyme digestion and nucleotide sequencing confirmed that the recombinant plasmids were correct. And we found that the human cyclin D1 and cyclin B1 fusion protein，with the right molecular weight，was expressed in transiently transfected HeLa cells. CONCLUSION：Recombinant cyclin D1 and cyclin B1 were successfully expressed，which laid foundation for further studies of these and their related proteins.

Key words: cyclins, vector construction, transient transfection, eukaryotic expression