AN ALTERNATIVE PATHWAY FOR YEAST TELOMERE MAINTENANCE RESCUES EST1- SENESCENCE

Yeast cells lacking a functional EST1 gene show progressive shortening of the terminal G1-3T telomeric repeats and a parallel increase in th e frequency of cell death. Although the majority of the cells in an es t1-culture die, a minor subpopulation survives the potentially lethal consequences of the est1 mutation. We show that these est1- survivors arise as a result of the amplification and acquisition of subtelomeric elements (and their deletion derivatives) by a large number of telome res. Hence, even when the primary pathway for telomere replication is defective, an alternative backup pathway can restore telomere function and keep the cell alive.