Objective        To preliminarily identify and characterize the core promoter region for human hyaluronan synthase 3 (HAS3) gene.        Methods        The previous constructed HAS3 promoter reporter

P(-761/-305)

was used as template to make four different deletion mutants and site-directed mutants by using PCR based site-directed mutagenesis. Dual luciferase reporter assay was used to determine promoter reporter activity.        Results        Four deletion mutants were constructed

including P(-761/-569)

P(-563/-305)

P(-490/-305) and P(-433/-305). Among the four deletion mutants

P(-761/-569) had no promoter activity whereas P(-563/-305)

P(-490/-305) and P(-433/-305) showed significant promoter activity. Site-directed mutagenesis of Sp1-binding site and core promoter element resulted in a decrease in HAS3 promoter activity.        Conclusion        The core promoter region of HAS3 gene is mainly located in a 129-bp region (-433 bp to -305 bp) nearby the major transcriptional start site. Sp1 might play an important role in the transcriptional regulation of HAS3 gene.