Submitted to: Molecular and Cellular Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/17/2000
Publication Date: 2/20/2001
Citation: Yamaguchi, H., Nagaoka, K., Imakawa, K., Sakai, S., Christenson, R.K. 2001. Enhancer regions of ovine interferon-tau gene that confer PMA response or cell type specific transcription. Molecular and Cellular Endocrinology. 173(1-2):147-155. Interpretive Summary: During early pregnancy, embryo loss is one of the most costly factors influencing the livestock industry. Such losses in sheep occur as a result of an impaired signal from the developing conceptus to the maternal system. In sheep, the gene controlling the conceptus signaling product (ovine interferon-tau, oIFNtau) is known. The objective of this study was to determine specific regions within the gene that control enhanced expressio of the signaling product in an uterine cell culture system. Results indicate that upstream regions between -654 and -555 bases were essential for enhanced oIFNtau gene expression. Enhancer sequences were recognized by cell nuclear extracts from developing sheep conceptuses. Gene expression by conceptus cells controls maternal recognition of pregnancy and implantation, and improvement in these processes can improve lambing rates for the U.S. sheep industry.
Technical Abstract: The molecular mechanisms regulating the temporal/spatial expression of the IFN-tau gene are not clearly understood. The 5'-upstream region of the sheep IFN-tau (oIFN-tau) gene was examined for its transcriptional regulation by deletion analysis in two different cell types; JEG3 cells supported the transactivation of oIFN-tau-receptor construct by HeLa cells did not. Enhancer elements required in JEG3 cells were localized between -654 and -555 bases, which were then inserted into a plasmid containing SV40 promoter and examined in a heterologous transcription system; high degrees of transactivation were observed in JEG3 cells and the activity was further enhanced by the addition of phorbol 12-myristate 13-acetate (PMA). However, similar responses were absent in HeLa cells, indicating cell specific enhancer activity. Sequential point mutations in the enhancer elements demonstrated that oIFN-tau enhancer-reporter constructs were primarily transactivated by three regions containing AP-1 site, GATA like sequence and a site(s) unidentified. Gel mobility shift assays (GMSAs) demonstrated that the AP-1 site located in the enhancer region was recognized by nuclear extracts from both cell types, but a GATA-like sequence exhibited different DNA-protein complex patterns in JEG3 and HeLa cells. Observations in which the same upstream sequence behaved differently due possibly to kinds of nuclear factors available in these cell lines suggest that such a sequence may be involved in cell specific transactivation of the oIFN-tau gene. Furthermore, the same enhancer sequences were also recognized by nuclear extracts from sheep trophoblasts, suggesting that the enhancer sequences between -654 and -555 bases of the oIFN-tau gene may be functioning in vivo.