The basal transcriptional activity of the murine TIEG1 gene is regulated by the transcriptional factor, JunB but not by the Sp1

초록

TIEG1,TGFβ inducibleearly1, is a member of the Sp1-like transcription factor family, which has been known as having an important role in cell proliferation, apoptosis, differentiation, and neoplastic transformation. Previously, it has been reported that a number of the conserved DNA sequences at the 5’upstream region of murineTIEG1 (mTIEG1) gene are identified but the basal transcriptional regulation mechanisms of these regions are unknown. Here, we characterized whether these regions were important in regulating the basal level transcription of the mTIEG1 gene. Seven deletions of 5’upstream DNA fragments fromthe 10kb mTIEG1 genomic DNA were produced by PCR and cloned into the upstream of the luciferase (Luc) reporter gene in the pGL3 basic plasmid. The luciferase reporter assay showed that the promoter of mTIEG1 gene at positions from -101 to +68 played an important role in the basal promoter activity of mTIEG1 gene. This region (-101/+68)contained the transcriptional factor binding motif, one JunB and two Sp1 sites. Mutationsat the JunB binding site, but not at the two Sp1 caused a dramatic decrease in the promoter activity. An electrophoretic mobility and super shift assays revealed that JunB protein specifically bound to this promote region. Taken together, our results suggest that the JunB but not Sp1 at mTIEG promoter may function as a positive regulatory factor for the basal transcriptional activity of mTIEG1 gene.