| Summary: | 碩士 === 國立臺灣大學 === 生化科學研究所 === 88 === Pregnancy-specific glycoproteins (PSGs) are primarily expressed in the placenta and become the major glycoproteins at term. To understand the function and regulation of PSG regulation in pregnancy, the promoter elements and cDNA sequences of a rodent PSG gene have been characterized. The cDNA of the rat pregnancy gene, rnCGM3, is 2761bp in length and contains an open reading frame that encodes a 475 amino acid polypeptide. The transcription initiation site of rnCGM3 is located at nucleotide —197 upstream of the translation start site.
Three nuclear protein binding sites: FPⅠ, FPⅡ and FPⅢ in 5’-flanking region of rnCGM3 gene have been characterized. The FPⅡ binding factor was shown to be C/EBPβ. RBPJκ was found to be the factor binds to both FPⅠ and FPⅢ. We also found another important transcription factor, the p65 subunit of NF-κB, which binds to the FPⅢ element in the yeast one-hybrid system. In this study, we showed that both p50 and p65 subunits of NF-κB bind to the FPⅢ element in the electrophoretic mobility shift assay (EMSA). A core sequence, 5'-GGGAAA-3', on the FPⅢ element for NF-κB was defined by mutagenesis analysis. Based on EMSA with NF-κB-enriched nuclear extracts from 293 cells transfected with different subunits of NF-κB, we found that both mono- and heterodimer of NF-κB bind to FPⅢ.
We further studied the effect of two different transcription factors, NF-κB and RBPJκ, on the regulation of rnCGM3 gene expression. By transient expression analyses, we found the expression of CAT reporter gene could be activated by p65 and this stimulatory effect of p65 could be repressed by RBPJκ. Our results suggest that rnCGM3 gene expression may be mediated by the NF-κB and the Notch signaling pathway via RBPJκ.
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