Addition of Telomerase to Somatic Cells

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Telomerase is an enzyme that is able to regenerate telomeres. In humans, it is found in some tissues, such as male germ cells, activated lymphocytes, and certain types of stem cell populations.[1][2][3] If present in somatic cells, it can turn them cancerous following mutation. Telomere shortening is one of the factors which contribute to aging so it is worthwhile to look into such an addition to develop anti-aging treatments.

Figure 1: Chromosome, telomere and telomerase shown together. Image was made by the Chopra Foundation


Telomeres are repeating sequences of nucleotides at the end of chromosomes which do not code for any proteins. This sequence has been identified to be "TTAGGC"[4][5]. Now, DNA polymerase is not capable of replicating the chromosome along its entire length. Hence every time DNA replications are undergone, the ends of chromosomes will be left out. Telomeres are extra sequences at those very ends so they can be lost instead of other vital protein-coding sequences. Leonard Hayflick demonstrated that a normal human fetal cell population will divide between 40 and 60 times in cell culture before entering a senescence phase. It occurs because each time a cell undergoes mitosis, the telomeres on the ends of each chromosome shorten slightly. Cell division will cease once telomeres shorten to a critical length. Hayflick interpreted his discovery to be aging at the cellular level.[6]


The molecular composition of the human telomerase complex was determined by Scott Cohen and his team at the Children's Medical Research Institute (Sydney Australia) and consists of two molecules each of human telomerase reverse transcriptase (TERT), telomerase RNA (TR or TERC), and dyskerin (DKC1).[7] That was the whole complex but the parts of telomerase of key interest include: one is the functional RNA component, hTERC which serves as a template for telomeric DNA synthesis: the other is a catalytic protein, hTERT with reverse transcriptase activity [8][9][10][11].The genes of telomerase subunits, which include TERT,[12] TERC,[13] DKC1[14] and TEP1,[15] are located on different chromosomes. The human TERT gene (hTERT) is translated into a protein of 1132 amino acids.[16] TERT polypeptide folds with (and carries) TERC, a non-coding RNA (451 nucleotides long).


Telomerase is a reverse transcriptase enzyme with its own RNA template. This makes it very similar to DNA viruses with the notable exception of capsids. Such similarities could be used to establish the idea that viruses may have fused with the cells of other organisms to give rise to telomerase in the course of evolution from the RNA world.[17]


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Edited by Nafeez Ishmam Ahmed, student of Joan Slonczewski for BIOL 116 Information in Living Systems, 2019, Kenyon College.