Sp1 and Sp3 transcription factors upregulate the proximal promoter of the human prostate-specific antigen gene in prostate cancer cells

The serum level of prostate-specific antigen (PSA) is useful as a clinical marker for diagnosis and assessment of the progression of prostate cancer, and in evaluating the effectiveness of treatment. We characterized four Sp1/Sp3 binding sites in the proximal promoter of the PSA gene. In a luciferase assay, these sites contributed to the basal promoter activity in prostate cancer cells. In an electrophoretic mobility shift assay and chromatin immunoprecipitation assay, we confirmed that Sp1 and Sp3 bind to these sites. Overexpression of wild-type Sp1 and Sp3 further upregulated the promoter activity, whereas overexpression of the Sp1 dominant-negative form or addition of mithramycin A significantly reduced the promoter activity and the endogenous mRNA level of PSA. Among the four binding sites, a GC box located at nucleotides -53 to -48 was especially critical for basal promoter activity. These results indicate that Sp1 and Sp3 are involved in the basal expression of PSA in prostate cancer cells.     

Induction of murine H-rev107 gene expression by growth arrest and histone acetylation: involvement of an Sp1/Sp3-binding GC-box

H-rev107 is downregulated in many carcinomas and tumor cell lines. Using postconfluent NIH3T3 cells, we demonstrated that growth arrest caused by contact inhibition, but not serum deprivation, increased H-rev107 expression. Furthermore, histone deacetylase inhibitors induced H-rev107 expression in NIH3T3 cells and allowed its reexpression in H-rev107-deficient WEHI 7.1 lymphoma cells. In contrast, no effect of the postconfluent stage or histone deacetylase inhibitors on H-rev107 levels was observed in tumorigenic H-rev107-expressing cell lines, HepG2, HeLa, and SKBR3. Transfections showed that TSA treatment increased luciferase activity 20-fold in NIH3T3 cells. We found that the GC-box at -83/-75 is a key element for H-rev107 induction by TSA and growth arrest, although there were no changes in the pattern and intensity of Sp1/Sp3-binding after induction. These data suggest that contact inhibition of growth and growth arrest caused by histone deacetylase inhibitors probably use the same mechanism to stimulate H-rev107 expression via histone acetylation in NIH3T3 cells and this might contribute to the development of drugs that can induce H-rev107 expression in certain tumors.