AUD4, a new amplifiable element from Streptomyces lividans

After transformation of the Streptomyces lividans chloramphenicol-sensitive , arginine-auxotrophic mutant strain AJ100 with a derivative of plasmid SCP 2, some of the regenerated protoplasts contained an 8.2 kb DNA sequence amp lified to several hundred copies per chromosome, The corresponding nonampli fied sequence, called AUD4, was isolated from a lambda phage genomic librar y of S. lividans 1326, Two cytosine residues were the only directly repeate d nucleotides at the ends of the element, indicating that AUD4 is a class I amplifiable sequence, The element mapped in the Asel-D fragment of the S. lividans chromosome, where other class I amplifications have been described , The complete element was sequenced and 10 ORFs were identified, Some of t he deduced proteins are highly conserved in other organisms but a putative function could be attributed to only a few of them, Duplication of AUD4 by integration of an Escherichia coli plasmid carrying various parts of AUD4 a nd a thiostrepton-resistance gene in S. lividans AJ100, ZX7 or TK64 induced amplification of the integrated plasmid, AUD4 or both at high frequency.