PURPOSE: To obtain a gene regulation cassette of readily manifesting an adventitious gene, containing lambda PR operator/promoter (RO/P), two pairs of bases at the 3' side of transcription initiation point of RO/P, etc.

CONSTITUTION: RO/P, two pairs of bases at the 3' side of transcription initiation point of RO/P or restriction site such as ClaI adjoining the two paris of bases is contained to prepare a gene regulation cassette (A) which comprises DNA sequence shown by the formula and is capable of detecting given mRNA sequence. Then the component A is connected to adventitious gene (B) selected from interleukin 1β (IL-1β) and M-CSF, etc., to give manifestation vector (C) of plasmid #595. Then the component C is transformed with a bacterium to give E coli S-#595(HB101) (ATCC No.67,755) strain (D). Optionally the strain D is cultured to produce interleukin 1β.