Telomerase

Telomerase, also called terminal transferase, is a special kind of ribonucleoprotein that helps keep our cells healthy. It adds a specific telomere repeat sequence to the ends of telomeres, which are protective caps on the tips of chromosomes. These telomeres guard the chromosome ends from damage.

Telomerase works as a reverse transcriptase enzyme, carrying its own RNA molecule to use as a pattern while it lengthens the telomeres. It is especially active in gametes, the cells that become eggs or sperm, and in many cancer cells. However, in most regular body cells, called somatic cells, telomerase is usually not present. This enzyme plays an important role in how cells age and stay healthy.

History

The idea that telomeres might help with aging was first suggested in 1973 by a scientist named Alexey Olovnikov. In 1984, Carol W. Greider and Elizabeth Blackburn discovered telomerase in a tiny organism called a ciliate. For this work, they later won a Nobel Prize in Physiology or Medicine together with Jack W. Szostak. Scientists have since learned more about how telomerase works in both simple organisms and humans, helping us understand its role in cell aging and cancer.

Structure

The main part of telomerase is a protein called telomerase reverse transcriptase. This protein helps add DNA sequences to the ends of chromosomes.

The full telomerase complex includes telomerase RNA, the telomerase reverse transcriptase protein, and several other helper molecules. They work together to protect chromosome ends. In humans, the complex also includes special proteins that bind to the RNA and help the enzyme work properly.

Mechanism

The protein TPP1 helps bring the telomerase enzyme to the ends of chromosomes, called telomeres. Telomerase uses a piece called TERC to add a special six-nucleotide sequence to the end of chromosomes. In animals, this sequence is TTAGGG.

Telomerase works by matching part of the template to the end of the chromosome, adding a new repeat, then moving to add more repeats. This helps keep the telomeres from getting shorter.

Clinical implications

Telomerase helps restore tiny bits of DNA called telomeres. These bits get shorter each time a cell divides. Normally, cells stop dividing when telomeres get too short. But telomerase lets cells keep dividing by adding back these bits of DNA.

This ability to divide forever is common in cancer cells, which helps them grow uncontrollably.

Embryonic stem cells, which develop into babies, have a lot of telomerase. In adults, only certain cells like sperm cells and some immune cells make telomerase. Most regular body cells don’t make much telomerase. Studies show that telomere length doesn’t always match an animal’s lifespan. Some researchers think telomerase might help fight aging, but it can also increase cancer risk. There are products on the market claiming to boost telomerase to delay aging, but their effects aren’t fully proven.

Certain rare diseases, like Werner syndrome and Progeria syndrome, are linked to shorter telomeres. These conditions may come from problems with DNA repair. Scientists are studying ways to block telomerase to treat cancer. Some treatments aim to weaken cancer cells by stopping telomerase activity.

TERT Splice Variants

Telomerase has different forms, called splice variants. These come from the same gene but are made in slightly different ways. These variants can change how well telomerase works. They might help normal cells grow or be involved in diseases like cancer. Scientists study these variants to learn more about how cells stay healthy and when they go wrong.