Telomeres are highly repetitive DNA sequences located in the terminal part of chromosomes.

They are formed by sequences of nucleotides TTAGGG.

Telomeres prevent the loss of information on chromosomes during DNA replication. This is due to the inability of DNA polymerase to replace the terminal primer of RNA with the respective sequence of DNA. Telomeres protect the coding information placed at the end of chromosomes from the loss of nucleotides.

Telomerase is an enzyme that adds non-coding DNA sequences, TTAGGG, to the strands of DNA in the regions of telomeres in order to avoid total loss of telomeres and further loss of coding information.

Telomerase is not the only enzyme that protects the integrity of telomeres. Other important enzymes that perform this task are contained in the Shelterin Complex. Shelterin proteins control the structure and the length of telomeres and they influence the telomeres activity.

A main function of this complex is to prevent the access of DNA repair proteins to the telomeres. Otherwise, telomeres would be repaired as DNA breaks leading to chromosome fusions. Shelterin proteins control the work of telomerase and they avoid the production of too long telomeres.

If the Shelterin Complex finds errors in the DNA, the complex acts on the cell with an efficient process of senescence and/or apoptosis making cell unable to reproduce or bringing it to a programmed death.

But when there is a malfunction of the complex, healthy cells go to death, or more often to premature aging due to the low amount of telomeres which prevent the loss of coding information.

Errors in the operation on the telomerase or the Shelterin proteins lead to early development of disease, such as pulmonary fibrosis or aplastic anemia.

Moreover various loss-of-functions models for Shelterin components are characterized by rapid decline of the regenerative capacity of tissue and accelerated aging, a phenomenon that occurs even in the presence of telomeres with a normal length.

Recent studies have sought a way to eliminate the malfunction of complex going to increase the production of telomeres by telomerase, but in many cases this has led to the formation of cancer because the large number of non-functioning cells and hardly destructible.