Telomere sequences attached to nuclearly migrated yeast linear plasmid

The yeast linear plasmid pCLU1, derived from pGKL1, has terminal proteins ( TPs) covalently attached at the 5' ends of inverted terminal repeats (ITRs) and replicates in the cytoplasm, presumably using the TP as a primer for D NA synthesis. In Saccharomyces cerevisiae, under certain conditions, pCLU1 migrated into the nucleus and replicated in either linear or circular form. The linear-form plasmid lacked TPs; instead it carried host-telomere repea ts at the ITR ends. The present study showed that (1) the added telomere wa s primarily composed of the repeated tracts of TGTGTGGGT-GTGG, which was co mplementary to the RNA template of yeast telomerase, (2) the telomeric addi tion occurred at the very end of the ITRs, and (3) the sequence composition of the added telomeres was diverse among individual plasmids, but symmetri cally identical at both ends of each plasmid. A similar mode of telomere ad dition was also observed in cells defective in the RAD52 gene. (C) 2000 Aca demic Press.