Different Epigenetic Status of Bovine Interferone-tau Gene in Trophoblast and Non-trophoblast Cells.

Abstract

Interferon-tau (IFNT), secreted by peri-implantation trophoblasts into the uterine lumen, is a major cytokine implicated in the process of maternal recognition of pregnancy in ruminant ungulates. Molecular mechanisms by which IFNT expression is regulated have been extensively investigated. However, epigenetic alterations such as aberrant DNA methylation and covalent histone modification that contributes to IFNT gene expression by altering chromatin conformation have not been well characterized. Using Chromatin Immunoprecipitation (ChIP) assay, we examined chromatin structures of the 5f-upstream regions and ORF of the bovine IFNT gene (IFN-tau-c1) in bovine-derived trophoblast cells, BT-1 cells and CT-1 cells, and non-trophoblast bovine cells, kidney MDBK cells, ovarian cumulus-granulosa (oCG) cells and ear fibroblast (EF) cells. ChIP assay was performed using antibodies against histone H3 acetyl K18 (H3K18ac) and H3 tri-methyl K4 (H3K4me3) as a marker for transcriptional active state, and histone H3 mono-methyl K9 (H3K9me) and histone H3 di-methyl K9 (H3K9me2) as a marker for transcriptional inactive state. Extensive signal were found for H3K18ac in trophoblast cells, BT-1 and CT-1, while very low signals were found in non-trophoblast cells, MDBK, oCG and EF. Very low signals for H3K9me were found on BT-1 and CT-1, whereas strong signals were detected in MDBK, oCG and EF. Acetylation of lysine residues, controlled by specific histone acetyltransferase (HATs) and histone deacetylases (HDACs), correlates with transcriptional activity in many genes. We, therefore, examined whether HDAC was involved in the silencing of IFNT gene in MDBK using ChIP assay with anti-HDAC-1 antibody and anti-HDAC-2 antibody. It was found that HDAC1 and HDAC2 bound to the 5f-upstream regions of bovine IFNT gene, whereas only HDAC1 bound to the IFNT fs ORF regions. These data show that recruitment of HDAC1 and/or HDAC2 stabilizes nucleosomes during transcription attenuation or repression, therefore, IFNT transcription may be repressed in non-trophoblast cells.