Objective    To investigate the activity of cyclin B1 promoter in different cell cycle of HeLa cells and to explore its regulation role on cyclin B1 protein.     Methods    The cyclin B1 promoter of HeLa cells was obtained by PCR amplification

and then the PCR product was inserted into the plasmid of pGL3 promoter vector by recombination to construct the plasmid of pGL3/cyclin B1 promoter. HeLa cells were synchronized in G

1

S

G

2

/M phase by hydroxyurea (HU)

which was then identified by flow cytometry. The plasmid of pGL3/cyclin B1 promoter was transiently transfected into HeLa c

ells. The dual luciferase assay was performed in the HeLa cells at G

1

S

or G

2

/M phase for the promoter activity.     Results    The activity of cyclin B1 promoter was highest in G

1

phase

decreased in S phase

and was medium in G

2

/M phase.     Conclusion    The activity of cyclin B1 promoter is different from the expression of cyclin B1 protein in the cell cycles of HeLa cells.