InterPro: IPR003545 Telomere reverse transcriptase

Telomerase is an enzyme that, in certain cells, maintains the physical ends of chromosomes (telomeres) during replication. In somatic cells, replication of the lagging strand requires the continual presence of an RNA primer approximately 200 nucleotides upstream, which is complementary to the template strand. Since there is a region of DNA less than 200 base pairs from the end of the chromosome where this is not possible, the chromosome is continually shortened. However, there is a surplus of repetitive DNA at the ends, the telomeres, that protects against the erosion of gene-encoding DNA.

Telomerase is a ribonucleoprotein (RNP) that synthesises the telomeric DNA repeats. The telomerase RNA subunit provides the template for synthesis of these repeats. There are 2 protein components of the RNP: the catalytic subunit is known as telomerase reverse transcriptase (TERT). The reverse transcriptase domain is located in the C-terminal region of the TERT polypeptide and single amino acid substitutions in this region lead to telomere shortening and senescence [1].

Telomerase is not normally expressed in somatic cells and it has been suggested that exogenous TERT may extend the lifespan of, or even immortalise, the cell. However, recent studies have shown that telomerase activity can be induced by a number of oncogenes [2]. Conversely, the oncogene c-myc can be activated in human TERT immortalised cells [3].