Palindromic protection

Research from Laura Maringele and David Lydall (University of Newcastle, UK) shows that yeast find a way to survive in the absence of telomeres. By forming large palindromes at chromosome ends, yeast mutants proliferate for many generations despite genomic instability, possibly becoming the yeast equivalent of cancer cells.

Chromosomes are progressively eroded with each cell cycle if they are not protected by telomeres, in part because the DNA replication machinery cannot copy the ends of linear DNA. Telomeres are maintained by telomerase or, when telomerase is compromised, by recombination. Maringele and Lydall now uncover a pathway to prevent chromosome shortening that is independent of both telomerase and recombination.

This pathway was seen in yeast mutants lacking the Exo1 nuclease. These mutants escape the cell cycle checkpoints that are normally activated by the loss...