Telomerase

Telomerase is a ribonucleoprotein complex that synthesizes DNA repeat sequences at chromosome ends, thereby preventing telomere shortening and playing a central role in determining cellular lifespan. This structure is active in numerous biological processes, primarily human cell division, aging, cancer, and immune system regulation. Telomeres consist of repetitive DNA sequences located at the ends of chromosomal DNA and shorten slightly with each cell division. In cells where telomerase is active, this shortening is counterbalanced; otherwise, the cell enters the aging process (senescence).

Structure and Components

Telomerase consists of two essential components:

• TERT (Telomerase Reverse Transcriptase): Provides enzymatic activity.
• TERC/hTR (Telomerase RNA Component): Serves as the RNA template for DNA synthesis.

Additionally, proteins such as dyskerin, NOP10, NHP2, and GAR1 bind to the telomerase holoenzyme to ensure structural stability and functional integrity.

Cellular Functions

The primary function of telomerase is to prevent telomere shortening during each cell division. This activity is particularly high in:

• Embryonic development,
• Adult stem cells,
• Certain immune cells (T and B cells),
• Cancer cells.

In normal somatic cells, telomerase remains inactive.

Alternative Functions of Telomerase

In recent years, roles of telomerase beyond telomere length maintenance have been identified. These “non-canonical” functions include:

• Regulation of cellular stress responses,
• Control of gene expression,
• Regulation of mitochondrial function,
• Enhancement of anti-apoptotic and antioxidant defenses.

Most of these functions are mediated through the TERT protein, and it has been demonstrated that TERT provides protection against oxidative damage, particularly in nerve cells.

Telomerase and Aging

Inadequate telomerase activity leads to replicative aging due to telomere shortening. This phenomenon becomes especially evident in conditions such as age-related decline of T cells in the immune system (immunosenescence). Aged T cells lose functionality, increasing susceptibility to infections, cancer, and chronic diseases. Reactivating telomerase activity holds potential for restoring the functionality of these cells.

A poster illustrating the relationship between telomerase and aging (generated by artificial intelligence).

Telomerase and Cancer

Telomerase is a primary driver of cellular immortality. In approximately 90% of human cancers, telomerase is reactivated through increased expression of the hTERT gene. This reactivation enables cancer cells to divide indefinitely. During this stage of oncogenesis, telomerase directly contributes to maintaining genetic stability, facilitating DNA repair, and preventing cellular aging. Therapeutic approaches targeting telomerase—such as antisense oligonucleotides, small molecule inhibitors, and immunotherapies—are currently under investigation in clinical trials.

A poster illustrating the relationship between telomerase and cancer (generated by artificial intelligence).

Telomerase, Mitochondria, and Stress Response

Telomerase has a bidirectional relationship with mitochondria. Under conditions of oxidative stress, the TERT protein translocates to mitochondria and limits oxidative DNA damage. Conversely, mitochondrial dysfunction can trigger telomere damage. This reciprocal interaction highlights the multifaceted nature of cellular aging.

Clinical and Societal Significance

Telomerase is viewed as a targetable molecule in cancer therapy, a tool in anti-aging strategies, and a promising avenue for reprogramming the immune system. However, excessive activation of telomerase may increase cancer risk; therefore, these therapeutic strategies must be developed with great caution.