Telomerase activity and telomeric states in cell proliferative and differentiative mechanisms.

Telomeres are DNA-protein complexes playing an important role in the maintenance of genome integrity. Telomerase is the enzyme acting as a template for addition of new telomeric repeats; this addition is essential for those cellular populations that have proliferative and differentiative potential. Telomerase and associated proteins are essential in response to DNA damage. Moreover, telomere-associated proteins as TRF2 are involved in all signalling transduction pathway which drive cellular proliferation and differentiation. In somatic cells, shortening of telomeres contributes to the onset of senescence or apoptosis; tissues which require cellular renewal express telomerase activity in order to compensate telomeric shortening. Telomerase activity remains detectable in adult stem cells populations and in cells with high proliferative potential. Reactivation of telomerase activity may be a pathogenetic characteristic of neoplastic cellular population favouring tumoral proliferation and progression.