A New Connection at Human Telomeres: Association of the Mre11 Complex with TRF2

It is generally assumed that the DNA damage responsepathways operating in eukaryotic cells are not activatedby natural chromosome ends. Eukaryotic chromosomesterminate in telomeres, nucleoprotein complexes thoughtto mask chromosome ends from the machinery that detects and repairs damaged DNA. Indeed, in yeast and human cells, deteriorated telomeres signal to factors thathave also been implicated in the cellular response toDNA damage (Sandell and Zakian 1993; Chin et al. 1999;Karlseder et al. 1999). The recent finding that the Mre11complex, a mediator of the cellular DNA damage response, is present at intact human telomeres (Zhu et al.2000) contradicts the simple view that telomeres maskthe chromosome end from recognition as a DNA break.Here, we discuss how the Mre11 complex could collaborate with telomeric proteins to protect chromosome endsand regulate the maintenance of telomeric DNA...