Telomere sequences attached to nuclearly migrated yeast linear plasmid.

Area of Science:

• Molecular Biology
• Yeast Genetics
• Telomere Biology

Background:

• The yeast linear plasmid pCLU1 replicates in the cytoplasm using terminal proteins (TPs) as primers.
• Under certain conditions, pCLU1 can enter the nucleus and replicate as a linear or circular molecule.
• Nuclear linear pCLU1 lacks TPs and instead acquires host telomere repeats at its inverted terminal repeats (ITRs).

Purpose of the Study:

• To characterize the telomere addition process in nuclear linear pCLU1.
• To determine the sequence and location of added telomeres.
• To investigate the mechanism of telomere acquisition in relation to yeast telomerase and DNA repair pathways.

Main Methods:

• Analysis of pCLU1 DNA sequences from Saccharomyces cerevisiae.
• DNA sequencing to identify telomere repeat composition and attachment sites.
• Comparison of telomere addition in wild-type and RAD52-deficient cells.

Main Results:

• The added telomeres primarily consist of TGTGTGGGTGTGG repeats, complementary to yeast telomerase RNA.
• Telomeric addition occurs precisely at the ends of the inverted terminal repeats (ITRs).
• Telomere sequences are diverse among plasmids but symmetrically identical at both ends of each plasmid.
• Similar telomere addition was observed in RAD52-deficient cells, suggesting a RAD52-independent mechanism.

Conclusions:

• Nuclear linear pCLU1 acquires telomeres via a mechanism involving yeast telomerase.
• Telomere addition occurs at the ITRs and is symmetrically established.
• The process appears to be independent of the RAD52 gene, a key component of homologous recombination.