Figure 1.

Schematic map of pSLA2-derived circular and linear plasmids. (A) pQC110, showing the E. coli pSP72 plasmid-derived segment and a pSLA2-derived DNA segment containing one functional 365-bp telomere (Qin and Cohen 1998) and one defective telomere containing only the terminal 56-bp sequence. Telomere ends are indicated by arrowheads. Relevant restriction endonuclease cleavage sites are shown. (B) pQC26, a pSLA2-derived linear plasmid isolated from S. lividans ZX7. Terminal protein (TP) is attached covalently to 5′ DNA termini. The locations of the melC (melanin-producing) and tsr (thiostrepton resistance) genes are shown, as are the locations of SacI cleavage sites. The plasmid contains two functional telomeres. Plasmid DNA was cloned in E. coli, linearized by treatment with DraI enconuclease, and introduced into ZX7 by transformation, as indicated in Materials and Methods.