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Different Levels of Ovine Interferon-tau Gene Expressions Are Regulated Through the Short Promoter Region Including Ets-2 Binding Site

Matsuda-Minehata, Fuko, Katsumura, Momoko, Kijima, Sho, Christenson, Ronald K., Imakawa, Kazuhiko
Molecular reproduction and development 2005 v.72 no.1 pp. 7
sheep, gene expression, interferons, promoter regions, recombinant DNA, reporter genes, chloramphenicol acetyltransferase, binding sites, transcription factors
Regulation of interferon-tau (IFN tau) production, a conceptus secretory protein implicated in the process of maternal recognition of pregnancy, has not been fully elucidated. Among more than 10 ovine IFN tau (oIFN tau) gene sequences characterized, approximately 75% of oIFN tau transcripts expressed in utero is derived from oIFN tau-o10 gene and amounts of transcripts from other oIFN tau genes such as oIFN tau-o8 or oIFN tau-o2 are minimal. It was hypothesized that the variation in expression levels exhibited by oIFN tau-o10 and oIFN tau-o8/-o2 genes was due to differences in the proximal promoter regions of these oIFN tau genes. To test this hypothesis, transient transfection experiments with human choriocarcinoma JEG3 cells were executed with deleted and/or mutated 5'-upstream regions of these oIFN tau genes attached to the chloramphenicol acetyltransferase (CAT) reporter gene. Because only the Ets-2 binding site located in the oIFN tau-o10 gene appeared to differentiate the expression levels of these constructs, the 6 base pair (bp) Ets-2 sequence from the oIFN tau-o10 gene inserted into the oIFN tau-o8/-o2 gene-reporter construct was examined. The insertion of this Ets-2 binding site into the oIFN tau-o8/o2-reporter construct failed to increase the degree of transactivation. Rather than this 6 bp sequence, a 22 bp sequence of the proximal promoter region, including the Ets-2 binding site, of the oIFN tau-o10 gene was required for oIFN tau-o8/-o2-reporter transactivation. By electrophoretic mobility shift assay (EMSA), nuclear protein(s) bound to this 22 bp from the oIFN tau-o10 and oIFN tau-o8/o2 genes differed. These results suggest that the short promoter region including the Ets-2 binding site, not the Ets-2 binding region itself, may determine different levels of oIFN tau gene expressions seen in utero.