INDUCIBLE TRANSCRIPTION OF THE DNAA GENE FROM STREPTOMYCES-LIVIDANS-66

The dnaA gene of Streptomyces lividans was cloned using the Escherichi a coli medium-copy-number vector pSU18 and E. coli strain TC1963, whic h can bypass the requirement for the DnaA protein. Its regulatory regi on was subcloned in the Streptomyces probe vector pIJ4083. Primer exte nsion and S1 mapping studies allowed the identification of a class I S treptomyces promotor (P2). An additional, previously unknown promoter type (P1) was found by S1 mapping. The presence of two DnaA box motifs between P1 and P2 suggests that the transcriptions of the S. lividans dnaA gene is autoregulated by its gene product. It was shown that the transcription of the dnaA gene is significantly induced by mitomycin C, an agent known to inhibit DNA replication. The data suggest that, a s in E. coli, one of the regulatory mechanisms governing the transcrip tion of the dnaA gene in S. lividans is probably related to the SOS re sponse network.