Secretory Expression of the Fusion Protein IFNβ-HSA in Pichia pastoris

Overlapping PCR technology was employed to splice IFNβand HSA genes in vitro. The spliced gene was inserted into Pichia pastoris secretory vector pPIC9K. The IFNβ-HSA gene was designed for secretory expression under the control of promoter AOX1 and Mat a signal peptide in pPIC9K. The recombinant plasmid pPIC9K/IFNβ-HSA was linearized by restriction enzyme SalI and transformed into Pichia pastoris KM71 by electroporation. The recombinant strains identified by G418 selection and confirmed by PCR analysis were induced by methanol to express fusion protein IFNp-HSA. SDS-PAGE and Western blot analysis of the fusion protein showed that the expressed fusion protein IFNp-HSA with an apparent 90kDa molecular weight had the antigenicity of HSA. The specific activity of culture supernatant was about 640IU/ml assayed by the standard amiviral activity test on WISH cells challenged with VSV virus.