Objective    To construct vectors with report gene containing klotho promoter segments in different lengths and identify their transcriptional activities in different cell lines.     Methods    Genomic DNA of human red cells was used as the template

and human klotho promoter segments in different lengths were amplified by PCR. The amplified products were named klothoⅠto Ⅳ and then respectively cloned into pGL3-Basic vectors with luciferase report gene to construct eukaryotic expression vectors. The recombinant vectors were respectively co-transfected with pRL-TK vectors into HEK293 and HeLa cells with Lipofectamine 2000. The transcriptional activities were analyzed by double luciferase method.     Results    The different length klotho promoter segments were successfully cloned and their expression vectors were successfully constructed by double digestion and sequencing. The sequence -504 to -6 may be a core promoter region of klotho. The activities of klotho I and klotho Ⅱ in the both cells were lower

and the activity of klotho Ⅲ in the both cell lines was higher (P0.05). The activity of klotho Ⅳ was maintained at a high level in HEK293 cells

but significantly the activity was decreased in HeLa cell (P0.01).     Conclusion    Its expression level of klotho is cell-specific and the sequence -973 to -504 may be responsible for the activity decrease of klotho Ⅳ in HeLa cells.