Construction of a synthetic messenger RNA encoding a membrane protein

Construction of a retrovirus capable of transducing and expressing genes in multipotential embryonic cells

Retroviral gene expression is inhibited in embryonal carcinoma (EC) cells. We have constructed a recombinant retroviral vector that is capable of expressing the neomycin-resistance (neo) gene in EC cells. The critical modification that permits expression of the neo gene is the insertion of a composite simian virus 40 early gene-herpes simplex virus type 1 thymidine kinase gene (SVtk) promoter 3' to the viral first intron and 5' to the neo gene. When the SVtk promoter is deleted, the recombinant retrovirus is either unable or extremely inefficient at expressing the neo gene in EC cells.

Glycosylation and processing of prepro-alpha-factor through the yeast secretory pathway

Events in the synthesis and processing of prepro-alpha-factor have been assessed with the aid of mutants blocked at various stages in the yeast secretory pathway. In normal cells treated with tunicamycin, a precursor accumulates which is identical in molecular weight to the primary translation product synthesized in vitro. At the restrictive temperature in a mutant blocked early in the pathway (sec53), a molecule of similar molecular weight accumulates. In mutants affecting translocation into (sec59) and passage from (sec 18) the endoplasmic reticulum, a glycosylated form of the precursor containing three N-linked core oligosaccharides accumulates; however, it appears that the signal peptide is not removed. The glycosylated precursor first experiences proteolytic processing when accumulated in a mutant (sec7) blocked at the stage of the Golgi apparatus. Substantially greater amounts of the mature pheromone are seen in mutants that accumulate secretory vesicles (sec1, sec2, sec3, sec5).