Figure 5.

Model illustrating possible interactions between ATM and ATR and telomere components in Arabidopsis. Interactions denoted by solid arrows have been described in yeast or mammals. Dashed lines show hypothetical interactions. We and others (d'Adda di Fagagna et al. 2004; this study) speculate that the interaction of ATM and ATR with telomere proteins inhibits activation of the DNA damage response. In plants lacking ATM and telomerase, progressive loss of telomeric DNA leads to an inadequate DNA damage response and an abrupt accumulation of cells with profound genome instability. ATR plays a different role at telomeres. The lack of ATR in plants deficient in telomerase results in an increased rate of telomere shortening. Accelerated telomere erosion may reflect greater vulnerability to nucleolytic attack due to diminished binding of ATR-associated telomere proteins (see text for details).