Biology
Telomerase's Role in Cellular Aging and Cancer
Quick fact
Telomerase is reactivated in about 85–90% of human cancers, allowing cancer cells to divide indefinitely.
Why this is interesting
Every time your cells divide, a tiny piece of your DNA gets clipped off. So why don't we all run out of genes long before we die?
Read the full explanation
Understanding Telomerase's Role in Cellular Aging and Cancer
Think of your chromosomes as shoelaces, and the plastic tips at the ends as telomeres. Just as the tips prevent the lace from fraying, telomeres protect the DNA from damage. However, during cell division, the DNA replication machinery cannot copy the very ends of the chromosomes. So with each division, telomeres get a little shorter. When they become too short, the cell senses danger and stops dividing—this is called replicative senescence, a critical part of cellular aging. Most normal cells have very low telomerase activity, so they can only divide a limited number of times (the Hayflick limit). But a few cell types, like stem cells, express telomerase, which extends telomeres and keeps them long, allowing many divisions.
A deeper explanation
Telomerase is a specialized reverse transcriptase that adds repetitive DNA sequences (TTAGGG in vertebrates) to the ends of chromosomes. It consists of two key components: a catalytic protein subunit (TERT) and an RNA template (TERC). The enzyme binds to the overhanging G-rich strand of the telomere, then uses its RNA template to synthesize new DNA repeats, thus elongating the telomere. In normal somatic cells, telomerase is silenced after embryonic development, leading to progressive telomere shortening and eventual senescence. In contrast, cancer cells often reactivate telomerase through mutations in TERT promoter or other mechanisms, enabling unlimited proliferation (immortality). This is why telomerase is a promising target for cancer therapy: inhibiting it could shorten cancer cells' telomeres and force them into senescence or apoptosis. However, care is needed because telomerase also plays roles in stem cell maintenance.