Dataset Information

RNA-template dependent de novo telomere addition.

ABSTRACT: De novo addition of telomeric sequences can occur at broken chromosomes and must be well controlled, which is essential during programmed DNA reorganization processes. In ciliated protozoa an extreme form of DNA-reorganization is observed during macronuclear differentiation after sexual reproduction leading to the elimination of specific parts of the germline genome. Regulating these processes involves small noncoding RNAs, but in addition DNA-reordering, excision and amplification require RNA templates deriving from the parental macronucleus. We show that these putative RNA templates can carry telomeric repeats. Microinjection of RNA templates carrying modified telomeres into the developing macronucleus leads to modified telomeres in vegetative cells, providing strong evidence, that de novo addition of telomeres depends on a telomere-containing transcript from the parental macronucleus.

SUBMITTER: Fuhrmann G

PROVIDER: S-EPMC4993297 | biostudies-literature | 2016 Aug

REPOSITORIES: biostudies-literature

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RNA-template dependent de novo telomere addition.

Fuhrmann Gloria G Jönsson Franziska F Weil Patrick Philipp PP Postberg Jan J Lipps Hans J HJ

RNA biology 20160119 8

De novo addition of telomeric sequences can occur at broken chromosomes and must be well controlled, which is essential during programmed DNA reorganization processes. In ciliated protozoa an extreme form of DNA-reorganization is observed during macronuclear differentiation after sexual reproduction leading to the elimination of specific parts of the germline genome. Regulating these processes involves small noncoding RNAs, but in addition DNA-reordering, excision and amplification require RNA t ...[more]

PMID: 26786510

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Project description:DNA double-strand breaks (DSBs) are toxic forms of DNA damage that must be repaired to maintain genome integrity. Telomerase can act upon a DSB to create a de novo telomere, a process that interferes with normal repair and creates terminal deletions. We previously identified sequences in Saccharomyces cerevisiae (SiRTAs; Sites of Repair-associated Telomere Addition) that undergo unusually high frequencies of de novo telomere addition, even when the original chromosome break is several kilobases distal to the eventual site of telomerase action. Association of the single-stranded telomere binding protein Cdc13 with a SiRTA is required to stimulate de novo telomere addition. Because extensive resection must occur prior to Cdc13 binding, we utilized these sites to monitor the effect of proteins involved in homologous recombination. We find that telomere addition is significantly reduced in the absence of the Rad51 recombinase, while loss of Rad52, required for Rad51 nucleoprotein filament formation, has no effect. Deletion of RAD52 suppresses the defect of the rad51Δ strain, suggesting that Rad52 inhibits de novo telomere addition in the absence of Rad51. The ability of Rad51 to counteract this effect of Rad52 does not require DNA binding by Rad51, but does require interaction between the two proteins, while the inhibitory effect of Rad52 depends on its interaction with Replication Protein A (RPA). Intriguingly, the genetic interactions we report between RAD51 and RAD52 are similar to those previously observed in the context of checkpoint adaptation. Forced recruitment of Cdc13 fully restores telomere addition in the absence of Rad51, suggesting that Rad52, through its interaction with RPA-coated single-stranded DNA, inhibits the ability of Cdc13 to bind and stimulate telomere addition. Loss of the Rad51-Rad52 interaction also stimulates a subset of Rad52-dependent microhomology-mediated repair (MHMR) events, consistent with the known ability of Rad51 to prevent single-strand annealing.

Dataset Information

RNA-template dependent de novo telomere addition.

Publications

RNA-template dependent de novo telomere addition.

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