干扰素-λs(Interferon-λs,IFN-λs)是近年来发现的一类新型干扰素,由于其兼具I型干扰素和白细胞介素(interleukin,IL)-10家族的双重特征,因此其成员的命名为IFN-λ1(IL-29)、IFN-λ2(IL-28A)和IFN-λ3(IL-28B)。IFN-λs的受体隶属于II型细胞因子受体家族(classII cytokine receptor family,CRF2),由特有的配基结合亚基CRF2-12/IFN-λR1(又称IL-28Rα)和辅助亚基CRF2-4(IL-10R2)组成。IFN-λs与I型IFN相同,均可通过激活JAK-STAT(janus kinase-signal transducer and activator of transcription)信号通路来传递配基结合信号,因此IFN-λs显示了与IFN-α相似的抗病毒、抑制肿瘤细胞生长以及具免疫调节功能等生物学活性,但由于其骨髓抑制及毒副作用少而生物学作用具长效性,且临床试验研究已经取得了突破性进展,故有望在不久的将来成为一个新的基因工程药物。
OBJECTIVE: To examine the feasibility of linking operons in tandem to enhance expression of heterologous genes in Escherichia coli (E. coli) and clarify the potential control mechanism of the total plasmid DNA amount ...
详细信息
OBJECTIVE: To examine the feasibility of linking operons in tandem to enhance expression of heterologous genes in Escherichia coli (E. coli) and clarify the potential control mechanism of the total plasmid DNA amount in each host cell. METHODS: Two series of expression plasmids, CW11 and CW12, containing 1 to 4 and 1 to 3 heterologous gene operon(s) respectively, were constructed. The molecular size of the CW11 series varied from 5.47 kb to 12.26 kb in 2.25 kb increments. The CW12 series varied from 5.40 kb to 9.72 kb in 2.16 kb increments. The expression level of desired protein was assayed by SDS-PAGE and laser density scanning. Plasmid copy number was determined by incorporation with (3)H-thymidine ((3)H-TdR). RESULTS: No influence of the tandem-joined operons on host growth and plasmid stability was observed. Upon induction, the desired protein accumulations in the CW11 series were 44.9% +/- 3.9%, 51.3% +/- 4.1%, 54.8% +/- 3.3% and 58.2% +/- 3.4% of total cell protein. In the CW12 series, the yields were 32.2% +/- 5.0%, 42.8% +/- 4.1% and 46.9% +/- 4.0% of total cell protein. As size increased, the plasmid copy number decreased, but target gene dosage increased significantly (P 0.05) and restricted to some extent. CONCLUSIONS: Increasing the target gene dosage by tandem linking of operons may enhance the expression level of a desired protein. Although the size (kb) and the copy number of each plasmid are negatively interrelated, for certain plasmids in each series, their total DNA amount per cell seems to be a restricted constant for specific E. coli strains under identical incubation condition.
暂无评论