engleski

Transformation with sequences from an AUD region in Streptomyces rimosus R6 induces DNA rearrangements

The oxytetracycline (OTC) gene cluster of S. rimosus R6 lies about 600 kb from one end of the linear chromosome in an amplifiable unit of DNA (AUD) (Pandza et al., Microbiol. 143, 1493, 1997). Constructs were designed to introduce disruptions or deletions into the chromosomal OTC cluster by homologous recombination. However, in nearly all cases (102 of 103 analysed) the transformants did not show the expected structure; they carried amplifications of the introduced genes and surrounding sequences or had deleted part or all of the OTC cluster. It is likely that these problems arise from the chromosomal location of the cluster. Deletions of about 750 kb in size occur that remove all the sequences from the chromosome end through the OTC cluster. The AUD gives rise to an amplified DNA sequence (ADS) of 250 kb which includes the OTC cluster. This is accompanied by deletion of distal sequences and probably leads to the replacement of the chromosome end by the ADS as suggested in S. lividans (Rauland et al., Mol. Gen. Genet. 246, 37, 1995). Thus, DNA rearrangements appear to be highly stimulated by integration of vectors carrying sequences from the AUD region.

Streptomyces; amplifiable unit of DNA; deletion; amplification

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