Construction Of A Base Expression Vector Directed By Goat β-casein Promoter And Its Transient Expression In Mammary Glands

The 1.132kb 5' promoter upstream regulatory sequence of the goat β-casein gene was amplified by PCR from the goat genome.The result showed that the sequence was exactly the same with which had been published in GenBank.In order to express valuable proteins in animal mammary glands, a base vector containing goat P -casein gene promoter, bovine growth hormone polyadenylation signal, matrix attachment region and multiple cloning sites was constructed. By adding linker 1 and Iinker2 with some clone sites, the vector was modified and may be used to establish mammary gland bioreactor.After being fused with tissue plasminogen activator cDNA, the vector was injected directly into the lactating mammary glands of goats. The transient expression results showed that the mammary specific expression vector driven by the goat P -casein gene promoter could efficiently direct the expression of tPA in goat milk, ranging from 2.0 to 6.9mg per liter. It was further found that the tPA was secreted stably during later stage of lactation. The expression level had direct correlation with the amount of DNA injected. The common transfection reagents such as span-glycerol did not have effect on the gene expression in this study.On the base of this study, a rapidly detection system from the goat beta-casein promoter and goat lactating mammary glands for mammary gland expression vectors was established. By using this system, some biologically active proteins may be produced conveniently.