| abstract |
IN ORDER TO MAKE A YEAST STRAIN CAPABLE OF EXPRESSING A DESIRED POLYPEPTIDE (E.G.LEUKOCYTE INTERFERON D) WHICH IT DOES NOT NORMALLY MAKE OR USE, IT IS TRANSFORMED WITH AN EXPRESSION VECTOR. THIS IS OBTAINED BY PRODUCING A TRANSFER VECTOR WHICH HAS RESPECTIVE ORIGINS OF REPLICATION AND PHENOTYPIC SELECTION GENES DERIVED FROM BOTH BACTERIA AND YEAST, AND INSERTING INTO IT DNA FRAGMENTS: (I) CODING FOR THE DESIRED POLYPEPTIDE; AND (II) COMPRISING A YEAST-DERIVED PROMOTER.THE INSERTION IS EFFECTED SO THAT 'START' AND 'STOP' SIGNALS ARE PROVIDED, AND THESE AND THE PROMOTER CAN CONTROL EXPRESSION OF THE POLYPEPTIDE, AND SO THAT THE REPLICATION ORIGINS AND PHENOTYPIC SELECTION GENES OF THE TRANSFER VECTOR ARE STILL FUNCTIONAL. THUS THE EXPRESSION VECTOR AND ITS PRECURSORS CAN REPLICATE, AND THEIR PRESENCE CAN BE RECOGNISED, BOTH IN YEAST AND BACTERIA. BACTERIA ARE USED FOR AMPLIFICATION. THE YEAST-DERIVED PHENOTYPIC SELECTION GENE MAY COMPLEMENT A MUTATION CARRIED BY THE STRAIN TO BE TRANSFORMED. |