The protein composition of human telomerase was identified in 2007 by Dr Scott Cohen and his team at the Children's Medical Research Institute in Australia. It consists of two molecules each of human Telomerase Reverse Transcriptase (TERT), Telomerase RNA (hTR or TERC) and dyskerin. The two types of protein subunits of the enzyme are coded by two different genes in the genome. The coding region of the TERT gene is 3396bp, and translates to a protein of 1131 amino acids. The polypeptide folds with TERC (451 nucleotides long), which is not translated and remains as RNA. TERT has a 'mitten' structure that allows it to wrap around the chromosome to add single-stranded telomere repeats.The enzyme telomerase allows for replacement of short bits of DNA known as a telomere, which are otherwise lost when a cell divides via mitosis.
In normal circumstances, without the presence of telomerase, if a cell divides recursively, at some point all the progeny will reach their Hayflick limit. With the presence of telomerase, each dividing cell can replace the lost bit of DNA, and any single cell can then divide unbounded. While this unbounded growth property has excited many researchers, caution is warranted in exploiting this property, as exactly this same unbounded growth is a crucial step in enabling cancerous growth.
Embryonic stem cells express telomerase, which allows them to divide repeatedly and form the individual. In adults, telomerase is highly expressed in cells that need to divide regularly (e.g., in the immune system), whereas most somatic cells express it only at very low levels in a cell-cycle dependent manner. (Source: Wikipedia)
