外源基因在甲醇酵母Pichia pastoris中的表达策略

Strategies for the Expression of Foreign Genes in the Methylotrophic Yeast Pichia pastoris

甲醇酵母 Pichia pastoris表达系统是近几年发展起来的一个真核表达系统 ,在其乙醇氧化酶基因启动子的控制下 ,某些外源基因的表达量可达克 /升以上。虽然该系统是一种优良的表达系统 ,但有许多因素影响外源基因在其中的表达 ,包括外源基因的拷贝数及其整合到酵母染色体的位置和方式、m RNA的 5′和 3′端非翻译区、转录起始密码子的上下文、外源基因 A+ T的组成与转录和翻译的阻断、密码子的偏爱性、信号肽序列的特性、产物的稳定性、宿主菌的生理特性、培养基成份和培养条件等。在应用该表达系统过程中 ,这些因素均需予以考虑。本文就这些因素作了概述和讨论 。

The methylotrophic yeast Pichia pastoris expression system has been developed recently. Under the control of the AOX1 gene promoter, foreign genes, such as tumor necrosis factor (TNF) and mouse epidermal growth factor (EGF), have been expressed at the level of up to more than 1 gram per liter medium in this system. Many factors influence the expression level of foreign genes in the system, including: copy number, A+T composition, and locus and mode of chromosomal integration of a foreign gene, context of start codon (AUG), 3 and 5 end of the untranslational region of mRNA, transcriptional and translational blocks, codon bias, nature of secretional signal, stability of the expressed products, physiological properties of the host yeast, medium composition and growth conditions, etc. All these factors should be taken into consideration to get optimal expression. The present paper reviewed and discussed some of these factors for the better understanding of the expression system.