Use of Avian Retro viral-Bovine Growth Hormone DNA Recombinants to Direct Expression of Biologically Active Growth Hormone by Cultured Fibroblasts

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Abstract
A variety of recombinant DNA molecules were constructed in which an avian retroviral long terminal repeat (LTR) was ligated to the bovine growth hormone (bGH) gene. The retroviral LTR was derived from a plasmid clone of a Schmidt Ruppin B strain of Rous sarcoma virus while the bGH gene was subcloned from a λ bacteriophage genomic library. Using a transient eukaryotic expression assay system, recombinant plasmid constructs were screened for their ability to direct expression and secretion of bGH. One such plasmid DNA construct, termed pBGH-4, was found to be active in the production of bGH. Stable mouse fibroblast cell lines were generated containing pBGH-4 DNA integrated into the mouse cell genome. Many of these mouse cell lines express and secrete bGH. One line, L-Pdλ-BGH4-13, was found to secrete bGH at a rate of 75 μg per 5 × 106 cells per 24 hr. Bovine growth hormone derived from this cell line is biologically active.