Abstract: A plasmid for a yeast host, the plasmid comprising in sequence: (1) a yeast derived promoter, (2) an albumin-encoding region placed under control of the yeast-derived promoter, (3) a transcription terminator and (4) a sequence homologous to a part of the yeast host chromosomal sequence such that the plasmid is capable of being integrated into the yeast host cell chromosome and wherein the plasmid is incapable of autonomous replication in yeast cells; a yeast host transformed with the above plasmid; a method of producing a yeast transformant which comprises transforming a yeast host by integrating at least two different plasmids each having a sequence homologous to a part of the host yeast chromosomal sequence one at a time into the chromosome of the yeast host cell; and a method of producing albumin which comprises cultivating the above transformant and recovering the thus-produced albumin.

Abstract: A mutant AOX2 (alcohol oxidase 2) promoter derived from the natural AOX2 promoter by base sequence deletion, insertion, or substitution is disclosed. A microbial strain carrying a gene under the control of such a mutant AOX2 promoter can be obtained by growing in a methanol-containing medium a strain incapable of producing AOX encoded by the AOX1 gene but carrying the AOX2 gene under the control of the natural AOX2 promoter. A heterologous protein may be produced by cultivating the mutant strain with the desired heterologous protein gene incorporated downstream from the mutant AOX2 promoter. A plasmid carrying the mutant AOX2 promoter is also provided.