Abstract: An improved promoter and a use thereof. An improvement is to mutate a nucleic acid sequence between ?35 region and ?10 region in a promoter region into recognition sites for an endonuclease. The improvement can overcome the problem that a strong promoter in a vector based on blue-white screening initiates the transcription or translation of foreign genes and a transcription or translation product might be toxic to a host and cannot be cloned, avoid the deficiency that frameshift mutation of a gene due to a lack of 1-2 bp of the vector at digestion sites results in false positive clones, and eliminate a false negative phenomenon that a plate is rich in blue spots due to a small fragment of foreign DNA and a reading frame of the gene which is unchanged by inserting the foreign DNA.

Abstract: An improved promoter and a use thereof. An improvement is to mutate a nucleic acid sequence between ?35 region and ?10 region in a promoter region into recognition sites for an endonuclease. The improvement is used for overcoming the problem that a transcription or translation product of foreign genes under a strong promoter might be toxic to a host and cannot be cloned and avoiding the phenomena of false positives and false negatives during blue-white screening.