Production of functional S-II in Bombyx mori cells

A cDNA for murine transcription factor S-II (Hirashima et al., J. Biol. Chem (1988) 263, 3858-3863) was inserted into a silkworm baculovirus vector and expressed in Bm-N cells, a cell line of Bombyx mori maintained in the laboratory. Recombinant S-II was purified from virus-infected cell extracts to near homogeneity by ammonium sulfate fractionation, and chromatographies on DEAE-cellulose and phosphocellulose. About 60 micrograms of recombinant S-II was obtained from 1 g of virus-infected cells. The molecular mass and specific activity of recombinant S-II were exactly the same as those of authentic S-II purified from Ehrlich ascites tumor cells.