Patent ID: 7316914

Claim:
An expression cassette for the expression of a nucleic acid of interest, the expression cassette including: a. at least one regulatory portion including: i. a first regulatory element which includes a nucleic acid sequences mmyR encoding an MmyR polypeptide and/or a nucleic acid sequence mmfR encoding an MmfR polypeptide; ii. a second regulatory element which includes the nucleic acid sequence mmfL encoding an MmfL polypeptide; and iii. a repressible promoter, the function of which is repressed by the expression product of the first regulatory element, that repression being alleviated or removed by a product, the production of the last-mentioned product being conferred by the MmfL polypeptide; and b. a heterologous nucleic acid of interest, in operative association with said promoter; wherein: said MmyR polypeptide shows at least 90% amino acid sequence identity with the sequence of SEQ ID NO: 12, optionally excluding the first 6 listed amino acids; said MmfR polypeptide shows at least 90% amino acid sequence identity with the sequence of SEQ ID NO: 11 said MmyR polypeptide and/or said MmfR polypeptide being effective to repress the function of said repressible promoter; and said MmfL polypeptide shows at least 80% 90% amino acid sequence identity with the sequence of SEQ ID NO: 17 said MmfL polypeptide being effective to produce said product which alleviates or removes repression of said repressible promoter by said MmyR polypeptide and/or said MmfR polypeptide.