Telomeres and Telomerase Activity Are Involved in Cancer and Aging
DNA is tightly coiled together to form chromosomes. Telomeres are located at the tips of the chromosomes that work with proteins to act as a cap for the chromosome structure. They prevent the tips of the chromosomes from sticking together. Another structural purpose of telomeres is that they are located at the end of the chromosome to prevent the rest of the chromosome from shortening and losing genes. Furthermore, telomeres are directly involved in DNA replication which ultimately results in cell division. Because of this, telomeres play a key role in aging and development of cancer throughout lifetime.
Upon successive cell division, telomere length decreases. When telomeres shorten too much, a cell becomes inactive or goes through apoptosis, or cell death. Telomeres are considered nature’s biological clock and gives insight into why humans are not immortal. For example, skin appears wrinkly with old age due to shortened telomeres. Blood cells and cells of the immune system are also affected by shortening of telomeres.
Telomeres are comprised of repeating DNA sequences. For humans, telomeres contain repeats of the nucleotide sequence TTAGGG paired with the sequence AATCCC on the other strand. Telomeres are partially prevented from shortening by an enzyme called telomerase, which adds short nucleotide sequences to 3’ ends of the DNA molecule. Telomerase contain RNA which acts as a template for synthesis of the repeat strands.
Cancer is noted as continuous growth of abnormal of cells in the body. With successive division of these cancerous cells, telomeres are shortened, causing cells to die. Activation of telomerase will prevent cells from shortening further. In this sense, cancerous cells have high telomerase activity because they grow continuously compared to normal cells. Telomerase activity and measurement of telomeres is a method to monitor the development of cancer.
People with malfunctioned telomeres experience premature aging, known as Werner’s syndrome. Those with Werner’s syndrome exhibit early physical characteristics of wrinkled skin, osteoporosis, graying hair, or cardiovascular disease. This syndrome is involved in an accelerated aging process because of rapidly increased shortening of telomeres. Though telomeres naturally shorten over time and contribute to physical characteristics of aging, telomeres are not the sole cause of aging and eventual death. Risk factors or family history of genetic disorder, DNA damage, and glycation, occurring from sugar binding to DNA, proteins and lipids making them unable to function, all play a role in aging. Further research into telomerase activity to prevent shortening of telomeres can result in the prolonging of human lifespan.