Ndj1p-dependent epigenetic resetting of telomere size in yeast meiosis.

Telomeres are essential for the protection of chromosomes against nucleases and recombinases and for the addition of G+T-rich simple sequence by the ribonucleoprotein reverse transcriptase telomerase . Telomere size instability and loss of telomerase activity in somatic cells is strongly associated with both oncogenesis and aging . Yet, an understanding of the mechanisms that maintain telomere size and structure during meiosis is still in its infancy . We have investigated the stability of single elongated telomeres during yeast meiosis. We find that elongated telomeres undergo high rates of precise deletion to wild-type telomere size via an intrachromatid pathway that shares properties with mitotic telomere rapid deletion (TRD). Loss of Ndj1p, a telomeric protein necessary for meiotic bouquet structure formation , confers a severe reduction in deletion rates. Return-to-growth (RTG) experiments suggest that deletion occurs at or near the period of meiotic recombination in NDJ1/NDJ1, but not in ndj1Delta/ndj1Delta diploids . We propose that Ndj1p facilitates deletion by promoting telomeric interactions during meiosis, resulting in an effective increase in the concentration of limiting factors for deletion.