In 1994, telomerase activity was discovered in human cancer cell lines. Although telomerase is not active in most human adult cells, all cells do contain the genes for telomerase proteins and telomerase RNA. Since inappropriate activation of telomerase may contribute to cancer, why do you think the genes coding for this enzyme have been maintained in the human genome throughout evolution? Are there any types of human body cells where telomerase activation would be advantageous or even necessary? Explain.

Key Concepts

Telomerase Function

Telomerase is an enzyme that adds repetitive nucleotide sequences to the ends of chromosomes, known as telomeres. This process helps maintain chromosome integrity during cell division, preventing the loss of essential genetic information. In most somatic cells, telomerase is inactive, leading to gradual telomere shortening and eventual cellular aging. However, in certain cells, such as stem cells and germ cells, telomerase activity is crucial for sustaining their ability to divide and differentiate.

Evolutionary Conservation

The presence of telomerase genes in the human genome suggests evolutionary conservation due to their essential role in cellular function. Evolution tends to preserve genes that confer a survival advantage, even if they are not actively expressed in all cell types. The maintenance of telomerase genes may reflect their importance in specific contexts, such as during embryonic development or in stem cells, where prolonged cell division is necessary for growth and tissue regeneration.

Cancer Biology

In cancer biology, the inappropriate activation of telomerase allows cancer cells to bypass normal cellular aging and continue dividing indefinitely. This uncontrolled proliferation is a hallmark of cancer, contributing to tumor growth and metastasis. Understanding the dual role of telomerase—beneficial in normal stem cells but potentially harmful in cancer—highlights the complexity of its regulation and the need for targeted therapies that can selectively inhibit telomerase in cancerous cells while preserving its function in healthy tissues.