Abstract
Gene expression of the porcine glycoprotein hormone α subunit (p-αGSU) was examined in LβT2 cells, which were established from the anterior pituitary lobe of the immortalized transgenic mouse and produce αGSU, and in CHO cells cloned from Chinese hamster ovaries. Expression of the reporter gene fused with p-αGSU gene upstream in LβT2 cells showed that the distal regions -540/-240 and -798/-541 are important for the activation of gene expression. In contrast, the transcriptional activity of the distal region of p-αGSU gene was repressed in CHO cells. The region -540/-240 contains an adequate enhancer, called pituitary glycoprotein hormone basal element, whereas the region -798/-541 has no distinguished element. Transfection of the expression vector containing cDNA of a pan-pituitary activator, Ptx1, whose putative binding sites are present scatted in the distal region of the p-αGSU gene, revealed unexpectedly that this factor significantly suppressed the expression of p-αGSU gene in LβT2 cells, indicating that Ptx1 is unrelated to the upregulation in the region -798/-541. Thus, this study demonstrated for the first time that the distal region -798/-541of the p-αGSU gene is indispensable for prominent expression of this gene in which an as yet unidentified factor may participate.
