engleski

DNA amplification in Streptomyces

DNA amplification consists of tandem repetition of chromosomal sequences and is common in Streptomyces species. We report experiments carried out in S. lividans 66, S. coelicolor A3(2) and S. rimosus R6. Amplification is often (but not always) accompanied by deletion of adjoining sequences to one side. It occurs in specific AUD (amplifiable units of DNA) regions. The AUD may be close (within 1 Mb) to one end of the linear chromosome, but can also be close to the middle of the chromosome. In the case of terminal AUDs all distal sequences are deleted up to the chromosome end. The structure formed does not enter PFGE gels and the copy number varies between about five and one hundred depending on the AUD. Amplifications can be stimulated by transforming with plasmids carrying sequences from an AUD region. This allowed mapping of the distal end of an AUD and the demonstration that amplification also occurs in circular chromosomes. The data will be discussed in the context of a model based on the stable DNA replication observed in E. coli adapted for the case of a linear chromosome.

Streptomyces; DNA amplification; DNA deletion

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