CELLULAR ROLE of TELOMERES

Abstract

Proliferation capacity of normal somatic cells are limited. The most important reason of it is the fact that, the structure called telomere which is consist of DNA repetition, gets shorter in every cell cycle and it limits cell replication. Telomeres are formed of many repetition of hexanucleotide series (TTAGGG)n. Mentioned hexanucleotides are located on the end of eukaryotic lineer chromosomes and they have no protein code. Morever, telomeres accompanied by many forms of specific proteins are necessary in order to prevent undesired effects such as edge-fusions and nucleotic effects, and it is also necessary in order to preserve genomic integrity. Cells with limited replication capacity enters in replicative ageing through shortening of telomeres in every consecutive cell division. These proliferatively incapacitated cells in the stage of irreversible ageing are metabolically active. It is reported that, in various diseases, age is the most important risk factor and there is a relation between the length of telomere and diseases depend on ageing. The preservation of telomere length and its stability is provided by telomerase enzyme complex which has its own RNA and proteins. In human cells, while telomerase enzyme activity is observed every region of body in first weeks of embryo, after that in most of the cells, the telomerase activity decreases depending on age factor. In time, some cells proliferate indefinably after telomerase enzyme regulation or reactivation. Cancer cells are this type of cells. Telomere shortening is considered to be an effective tumor supressor mechanism.