| Summary: | 碩士 === 國立臺灣大學 === 微生物學研究所 === 90 === Telomere maintenance is required for chromosome stability. Telomeres are replicated typically by the action of the reverse transcriptase, telomerase. In cells that lack telomerase, telomeres are maintained by an alternate recombination mechanism for survivor formation. Using an assay to trace the in vivo recom- bination products throughout the course of survivor development, we show here that telomere recombination may initially occur on only one telomere then spread to the remaining ends. The three major replicative polymerases a, d and e are required for telomere-telomere recombination and each exhibit a different phenotype when they are defective along with telomerase. Polymerase d provides the activity for long tract extension. While the polymerase d mutant completely lacks the long telomere and subtelomere lengthenings, polymerase a and e mutant each prefers to develop a type of survivors. Furthermore, telomere-telomere recombination is dependent on the cell-cycle checkpoint protein Tel1 and Mec1, and is regulated by telomeric binding protein Cdc13 and Ku complex. Such coordination between DNA replication machinery, DNA damage signaling, DNA recombination machinery, and telomere protein-DNA complex allows telomere recombination to repair telomeric ends in the absence of telomerase.
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