Telomerase 1984 – A New Therapeutic Target for Many Diseases

Each chromosome in our cells consists of a long, helical  DNA molecule wrapped around a protein scaffold. At the end of every chromosome is a  telomere, a special protective cap containing a sequence of bases represented by TTAGGG. 

The enzyme copying DNA for cell division cannot fully copy the end of each chromosome, but telomeres compensate for this potential defect. The terminal pieces are simply TTAGGG, potentially repeated more than 1000 times. However, a portion of the telomere is lost through this erosion at every cell division. When it becomes too short, the chromosome can no longer be copied in these  “old”  cells. Many body cells enter senescence, an inability to divide, after about 50 divisions in a culture dish.

In 1984, while studying the microscopic, single-celled  Tetrahymena, biologists Carol Greider and Elizabeth Blackburn discovered telomerase, an enzyme with an RNA component that prevents chromosome erosion and lengthens telomeres by adding TTAGGG back to chromosome ends.

Telomerase  activity  is very low in most somatic, non-reproductive cells, but active in fetal cells, adult germ cells producing sperm  and eggs, immune-system cells and tumour cells, all of which can divide regularly. 

These discoveries suggest  a link between telomerase activity, ageing and cancer. Consequently, to extend lifespan by making cells immortal or inhibit cancers by altering immortality and making cells divide into cells that can die, the idea of triggering  telomerase activation or inactivation  is being tested in a variety of experiments. 

Some premature-ageing diseases in humans are associated with short telomeres, and telomerase activation has been found in most human tumours. It should also be remembered that the single-celled freshwater organism  Tetrahymena  has active telomerase and can divide indefinitely, making it effectively immortal.

Greider and Blackburn said: 

“In the early 1980s, scientists studying chromosome maintenance in Tetrahymena were not trying to identify potential anticancer treatments... In studies of nature, one can never predict when and where fundamental processes will emerge.”

Description of the article image: Mice engineered to lack telomerase age prematurely, but their health is restored when the enzyme is replaced. Researchers can use specific stains to study bone and cartilage development and degeneration in mice.

Historical figures mentioned in the article: Elizabeth Helen Blackburn (b. 1948), Carolyn Widney “Carol” Greider (b. 1961)

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