Kozak序列+4G提高绿色荧光蛋白在HEK293细胞中的表达

构建含不同Kozak序列的绿色荧光蛋白(GFP)基因真核表达载体, 并检测它们在HEK293细胞中的表达差异。 通过设计突变的PCR引物改变目的基因GFP的Kozak序列, +4 位碱基分别为A和G, 且不改变氨基酸编码, 将PCR扩增的GFP片段与载体pcDNA3.1进行酶切、连接、转化、鉴定。成功构建的pHGFP-A, pHGFP-G质粒采用脂质体法转染HEK293细胞, 荧光显微镜下观察绿色荧光表达, 流式细胞术检测目的蛋白GFP的荧光表达阳性率, Western blot检测目的蛋白GFP的表达。构建的两质粒均能有效转染 HEK293细胞, 其中流式细胞术分析显示: pHGFP-A组GFP阳性率约为15%, pHGFP-G组GFP阳性率约为45%; Western blot 显示pHGFP-G的GFP表达量约为pHGFP-A的GFP表达量3.87倍。结果表明, Kozak序列+4G(?3位为嘌呤碱基时)在蛋白表达中发挥重要作用, 可以使绿色荧光蛋白GFP在HEK293细胞中的表达量提高约4倍。

Enhancement of GFP Expression by Kozak Sequence +4G in HEK293 Cells

To investigate the effect of Kozak sequence (+4A or +4G) on expression of green fluorescent protein (GFP) gene in HEK293 cells. The eukaryotic expression vectors containing GFP gene with different Kozak sequence (+4A or +4G) were constructed by classic DNA recombination methods, including PCR, enzyme digestion, ligation, transformation, identification, et al. Two different Kozak sequences (+4A or +4G) were obtained through PCR with different mutagenic primers. The right recombinant plasmids pHGFP-A and pHGFP-G were transfected into HEK293 cells by liposome-mediated gene transfer method. The expression level of GFP was observed by fluorescent microscope, flow cytometry and Western blot. The flow cytometry revealed that the expression levels of GFP fluorescence in pHGFP-A and pHGFP-G transfected cells were about 15% and 45%, respectively. Western blot showed the specific bands of about 27 kD (GFP) both in pHGFP-G and pHGFP-A sample lanes; and the GFP expression density of pHGFP-G was about 3.87-fold as that of pHGFP-A by ImageJ software analysis. These results indicated that the +4G in Kozak sequence (when ?3 site is purine base pair) plays an important role in GFP protein translation, which enhances the GFP expression up to 4-fold in HEK293 cells.