Telomerase+in+Cells

Cells Which Produce Telomerase:
All cells in the body are capable of producing telomerase, however not all do [4] [5]. Cells that commonly produce telomerase include gametes (sex cells), stem cells and immune cells [3] [6] [7]. This is because the functions of these cells are carried out over the long term, so these cells must be able to proliferate constantly to last out their roles [6]. Most other body cells, or somatic cells, do not produce telomerase [4] [5]. The function of somatic cells is simply to replace damaged cells, so these cells do not need to extend their life in order to do this [4] [5].

Cancer Cells and Telomerase:
Cancer cells have been found to produce telomerase [3] [8]. This is because one specific checkpoint in the cell cycle these cells bypass is one that tells the cell to stop dividing after its telomere becomes too short [2] [6]. Cancer cells do not receive this message and therefore continue to divide [2] [6]. A hypothetical model of this process is shown in Figure 1 below. The cells then produce telomerase and essentially become "immortalised", meaning they can divide indefinitely [1] [2] [5]. For this reason, the telomeres of cancer cells are significantly shorter than in normal somatic cells, and their constant production of telomerase can be a useful biomarker in identifying cancerous cells [1] [2] [4] [5] [7].

Figure 1: Hypothetical model of cancer cell formation (Picture obtained from Dahse, Fiedler and Ernst 1997) By Ashlea Norton //Last edited 11/11/2011//

References:
[1] Dahse, R., Fiedler, W. & Ernst, G. 1997, "Telomeres and Telomerase: Biological and Clinical Importance", //Clinical Chemistry, // vol. 43, no. 5, pp. 708-714.

[2] Greider, C.W. & Blackburn, E.H. 1996, "Telomeres, Telomerase and Cancer", //Scientific American,// vol. 96, no. 2, pp. 92.

[3] Hodes, R.J. 1999, "Telomere Length, Aging and Somatic Cell Turnover", //The Journal of Experimental Medicine,// vol. 190, no. 2, pp. 153-156.

[4] Shay, J.W., Zou, Y., Hiyama, E. & Wright, W.E. 2001, "Telomerase and Cancer", //Human Molecular Genetics,// vol. 10, no. 7, pp. 677-685.

[5] Wai, L.K. 2004, "Telomeres, Telomerase and Tumorigenesis - A Review", //Medscape General Medicine,// vol. 6, no. 3, pp. 19.

[6] Wright, D.L., Jones, E.L., Mayer, J.F., Oehninger, S., Gibbons, W.E. & Lanzendorf, S.E. 2001, "Characterisation of Telomerase Activity in the Human Oocyte and Preimplantation Embryo", //Molecular Human Reproduction,// vol. 7, no. 10, pp. 947-955.

[7] Zvereva, M.I., Shcherbakova, D.M. & Dontsova, O.A. 2010, "Telomerase: Structure, Functions, and Activity Regulation", //Biochemistry (Moscow),// vol. 75, no. 13, pp. 1563-1583.