Patent ID: 6090574
Filing Date: 2000-07-18
Classification: C12N

Abstract:
In a process for preparing a protein by a fungus transformed by multicopy integration of an expression vector in the ribosomal DNA of the fungus,the expression vector including in addition to an expressible structural gene encoding the protein an expressible deficient selection marker gene needed for the production of an ingredient essential for growth of the fungus, the essential ingredient being selected from the group consisting of amino acids, vitamins and nucleotides, said fungus having been modified prior to transformation to inactivate the wild type gene corresponding to said expressible deficient selection markerthe improvement wherein fungal cells are maintained with high copy number integrants, and consequent improved production of the protein, by growing the fungus at a growth rate at which uptake of the essential ingredient from the medium by the fungal cells is insufficient and intercellular de novo synthesis of the essential ingredient is required to maintain the growth rate,whereby cells with high copy number integrants are preferentially maintained over cells with low copy number integrants, whereby the production of the protein is improved.