The Expression Mechanism Of Human Chorionic Gonadotropin In Chinese Hamster Ovary Cells

Human chorionic gonadotropin (hCG) is a glycoprotein hormone that were synthesised and secreted by the placenta trophocyte cell. It play an important role in the female infertility, inducing ovulation, and detection of some diseases. For more than25years, hCG extracted from urine from pregnant women. Urinary preparations, however, are associated with a number of disadvantages, including an uncontrolled source, lack of purity, and batch-to-batch variation in activity leading to variable clinical results. Currently, the recombinant hCG have existed. Due to the lack of the understanding of the regulation mechanism of protein expression, the expression level of protein is so low. The cell lines which were able to express hCG stability were screened by Flp-InTM system. We mainly researched its entire expression process which included the abilities of transcription, transferring mRNA to polypeptide, assembling and secretion by using cell lines at the high and low-producing levels.Firstly, we measured the mRNA abundance of the two cell line, the half-life of the mRNA and the transcription rate. Then, we measured the concent of a subunit and β subunit polypeptide of hCG and the hCG protein using ELISA. In the study, we revealed the limitation of the expression of the hCG.Fristly, both of the two cell lines performed that the mRNA level of β subunit was higher than that of a subunit. So, higher (3subunit mRNA abundance was likely to essential for the hCG expression. Secondly, compared the mRNA ratio of the β subunit to a subunit, in the high-producing cell line the initial limitation may be at the level of transcription of a subunit. Thirdly, we demonstrated that for the high-producing cell line, transferring mRNA to polypeptides limitations prevented the cells from using the full expression potential generated at the mRNA level, especially β subunit. This may be related to the structure of β subunit. We knew that the β subunit contained more one disulfide bonds and four glycosylation sites than a summit. The lack of O-glycosylationsugar modification could be the main reasons for this limitation. Fourthly, there was no bottleneck at the level of assembling and secretion.In the study, we proposed a method of expression mechanism research and indenfied the limitations of the hCG expression. It played a guide role for the constrcting of engineering cell line that expressed the hCG.