Transcriptional Regulation of the Pregnancy-Specific Glycoprotein 5 Gene. Role of the Ubiquitous Sp1 Transcription Factor

NORES, R.; BLANCHON, L.; PATRITO, L.C.; SAPIN, V.; PANZETTA-DUTARI, G.

Villa Carlos Paz

Congreso; XXXVIII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2002

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB)

The human pregnancy-specific glycoprotein 5 gene (PSG5) expression is maximal in placenta and is regulated mainly during transcription. Its minimal promoter lacks TATA-box but contains a GC-like box acting as a core promoter element (CPE), which is active in both PSG-producing and non-producing cell lines. The proximal 5´ regulatory region bears at least two positive (FP1 and FP2) and two negative (FP3 and FP4) cis-acting elements recognized by placental and non-placental nuclear proteins. To get further insight into the regulatory factors involved in PSG gene expression, we have now investigated the nature of the transcription factors that recognize the CPE and the FP1 cis elements in placenta and COS7 cells, which do not express endogenous PSG genes. Gel-shift, supergel-shift, UV-crosslinking and southwestern-blot experiments clearly demonstrate that the ubiquitous Sp1 protein is the major transcription factor involved in complex formation with both cis-acting elements. Furthermore, transfection experiments indicated that Sp1 is able to transactivate PSG5 promoter constructs in COS7 and SL2 cell lines. In addition, we show that Sp1 is indeed co-expressed with PSG genes in the syncytiotrophoblast cells, stressing its potential role in vivo. We propose that the interaction of the Sp1 ubiquitous factor with other transcription factors is involved in the tissue-specific regulation of PSG5 gene.