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TelomereBecause of the way DNA replicates, telomeres are shortened each time a cell divides. Research suggests that the progressive shortening of the telomere then imposes a limit on the cell's ability to divide, and thus on maximum human life extension potential. In research, when normal somatic cells are transformed in the laboratory with DNA expressing high levels of telomerase, the enzyme that extends the telomere, they continue to divide by mitosis long after the replicative limit should have set in. And they do so without any further shortening of their telomeres. The research that showcased this was reported by Bodnar et. al. in the 16 January 1998 issue of Science. The anti aging potential in terms of extending life on cellular level is tremendous. However, there is also the potential to find new ways to combat cancer with the control of the telomerase enzyme. This is because one of the crucial features that distinguishes a cancer cell from a normal cell is its ability to divide indefinitely, most having the ability to synthesize high levels of telomerase and being able to prevent further shortening of their telomeres. Telomere - StudiesA.G. Bodnar, et al., "Extension of life-span by introduction of telomerase into normal human cells," Science, 279(5349):349-52, 16 January 1998. Greider, C.W. & Blackburn, E.H. (1985) "Identification of a specific telomere terminal transferase activity in Tetrahymena extracts." Cell v.43, (2 Pt. 1) pp. 405-413. Blasco MA. Telomeres and human disease: ageing, cancer and beyond. Nat Rev Genet. 2005 Aug;6(8):611-22. Yamaguchi H, Calado RT, Ly H, Kajigaya S, Baerlocher GM, Chanock SJ, Lansdorp PM, Young NS. Mutations in TERT, the gene for telomerase reverse transcriptase, in aplastic anemia. N Engl J Med. 2005 Apr 7;352(14):1413-24. Zhang A, Zheng C, Hou M, Lindvall C, Li KJ, Erlandsson F, Bjorkholm M, Gruber A, Blennow E, Xu D.Deletion of the telomerase reverse transcriptase gene and haploinsufficiency of telomere maintenance in Cri du chat syndrome. Am J Hum Genet. 2003 Apr;72(4):940-8. Epub 2003 Mar 10. Marrone A, Walne A, Dokal I. Dyskeratosis congenita: telomerase, telomeres and anticipation. Curr Opin Genet Dev. 2005 Jun;15(3):249-57. Armanios M, Chen JL, Chang YP, Brodsky RA, Hawkins A, Griffin CA, Eshleman JR, Cohen AR, Chakravarti A, Hamosh A, Greider CW. Haploinsufficiency of telomerase reverse transcriptase leads to anticipation in autosomal dominant dyskeratosis congenita. Proc Natl Acad Sci U S A. 2005 Nov 1;102(44):15960-4. Bryan TM, Englezou A, Gupta J, Bacchetti S, Reddel RR. Telomere elongation in immortal human cells without detectable telomerase activity. EMBO J. 1995 Sep 1;14(17):4240-8. Collins K. The biogenesis and regulation of telomerase holoenzyme Mol. Cell. Bio. Nature 7 , 484-494[2006].
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