Telomeres, telomerase, and aging

Abstract

We present a list of basic functions to ensure viability of living systems and highlight the roles that telomerase plays. Telomere length is an intrinsic determinant of cellular and perhaps organismal lifespan. The limitation of DNA polymerases in replicating the end of linear replication is partly taken care of by addition of hexanucleotide repeats at the end of the template strands by telomerase reverse transcriptase. Interaction of telomerase with other cellular molecules enables it to perform several extra-curricular functions. It is essential for dividing cells such as those of developing embryo, activated immune cells, activated stem cells, and cancerous cells, to have active telomerase in them. Telomere length is a qualifying feature to monitor cellular health and let it proceed along cell cycle, and hence telomerase takes the center stage and communicates with diverse cellular phenomena involving key regulators like transforming growth factor B, translationally controlled tumor protein, survivin, and p53. It is an anti-apoptotic factor and promotes cell survival. It also influences redox homoeostasis of cells. Genetic and environmental factors influencing telomerase expression can influence the aging process. We also comment on the relevance of telomerase as a therapeutic target in cancers that necessarily depend on maintenance of telomere length.