Transient gene expression in suspension HEK-293 cells: application to large-scale protein production.

Recent advances in genomics, proteomics, and structural biology raised the general need for significant amounts of pure recombinant protein (r-protein). Because of the difficulty in obtaining in some cases proper protein folding in bacteria, several methods have been established to obtain large amounts of r-proteins by transgene expression in mammalian cells. We have developed three nonviral DNA transfer protocols for suspension-adapted HEK-293 and CHO cells: (1) a calcium phosphate based method (Ca-Pi), (2) a calcium-mediated method called Calfection, and (3) a polyethylenimine-based method (PEI).

The CELO adenovirus Gam1 protein enhances transient and stable recombinant protein expression in Chinese hamster ovary cells.

The Gam1 protein of the avian CELO adenovirus activates transcription through inhibition of histone deacetylase 1 (HDAC1). We investigated the effect of Gam1 on both transient and stable transgene expression in Chinese hamster ovary (CHO) cells, one of the most commonly used mammalian hosts for the large-scale production of recombinant proteins. Transient expression of Gam1 increased reporter protein levels up to 4-fold in suspension cultures of CHO DG44 cells co-transfected with a reporter gene and up to 20-fold in recombinant CHO DG44-derived cell lines.

Physical interaction of human T-cell leukemia virus type 1 Tax with cyclin-dependent kinase 4 stimulates the phosphorylation of retinoblastoma protein.

The Tax oncoprotein of human T-cell leukemia virus type 1 (HTLV-1) induces leukemia in transgenic mice and permanent T-cell growth in vitro. In transformed lymphocytes, it acts as an essential growth factor. Tax stimulates the cell cycle in the G(1) phase by activating the cyclin-dependent kinase (CDK) CDK4 and CDK6 holoenzyme complexes.

Tax-dependent stimulation of G1 phase-specific cyclin-dependent kinases and increased expression of signal transduction genes characterize HTLV type 1-transformed T cells.

Human T cell leukemia virus protein induces T cells to permanent IL-2-dependent growth. These cells occasionally convert to factor independence. The viral oncoprotein Tax acts as an essential growth factor of transformed lymphocytes and stimulates the cell cycle in the G(1) phase.