Telomerase, mitochondria and oxidative stress.

Telomerase plays an important role in cellular proliferation capacity and survival under conditions of stress. A large part of this protective function is due to telomere capping and maintenance. Thus it contributes to cellular immortality in stem cells and cancer. Recently, evidence has accumulated that telomerase can contribute to cell survival and stress resistance in a largely telomere-independent manner. Telomerase has been shown to shuttle dynamically between different cellular locations. Under increased oxidative stress telomerase is excluded from the nucleus and can be found within the mitochondria. This phenotype correlates with decreased oxidative stress within telomerase expressing cells and improved mitochondrial function by currently largely unknown mechanisms. Our data suggest that mitochondrial protection could be an important non-canonical function for telomerase in cell survival and ageing. This review summarises briefly our knowledge about extra-telomeric functions of telomerase and discusses the potential significance of its mitochondrial localisation.