Exp Mol Med.  2004 Aug;36(4):300-310.

Weakening of the repressive YY-1 site on the thrombospondin-1 promoter via c-Jun/YY-1 interaction

• Kang JH
• Chang SY
• Yeom DH
• Kim SA
• Um SH
• Hong KJ

Abstract

Thrombospondin-1 (TSP-1) level is tightly regulated at the transcriptional level. To determine the detailed molecular mechanisms of TSP-1 expression, nine serial 5'-deletion constructs of the human genomic tsp-1 promoter (nucleotides -2,220 to +756) were prepared, inserted into luciferase reporter plasmids, and transiently transfected into the Hep3B human hepatocarcinoma cell. Among the nine 5'-deletion constructs, pTSP-Luc-4 (-767~+756) had consistently decreased luciferase activity with or without PMA stimulation, whereas a further truncated construct [pTSP-Luc-4' (-407~+756)] had increased levels of expression. By searching the nucleotides from -767 to -407, a consensus binding sequence (5'-CCATTTT-3') for the repressor Yin Yang-1 (YY-1) at nucleotide -440 was identified. The suppression induced by this site was weakened in the presence of the region upstream of nucleotide -767 (pTSP-Luc-1 and -2). Nuclear protein directly bound to an oligonucleotide containing the repressive YY-1 sequence but the binding capacity of the sequence was decreased by the increased c-Jun levels. Moreover, proteins immunoprecipitated with anti-YY-1 revealed an interaction between c-Jun and YY-1 factor. These data suggest that the repressive YY-1 site of the tsp-1 promoter could not be functional via activating positive cis-elements on the upstream from this site and weakened via c-Jun/YY-1 interactions.

Keyword

c-Jun; gene expression; promoter; TSP-1; YY-1

MeSH Terms

Binding Sites/genetics
Cell Line, Tumor
DNA-Binding Proteins/*metabolism
Down-Regulation/genetics
Electrophoretic Mobility Shift Assay
Genes, Reporter/genetics
Humans
Luciferases/analysis/genetics
Promoter Regions (Genetics)/*genetics
Proto-Oncogene Proteins c-jun/genetics/*metabolism
Repressor Proteins/*metabolism
Research Support, Non-U.S. Gov't
Sequence Deletion/genetics
Thrombospondin 1/*genetics/metabolism
Transcription Factor AP-1/metabolism
Transcription Factors/*metabolism