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TELOMERLERİN HÜCRESEL ROLÜ

CELLULAR ROLE of TELOMERES

Journal Name:

  • İstanbul Üniversitesi Diş Hekimliği Fakültesi Dergisi

Publication Year:

  • 2007

Key Words:

Keywords (Original Language):

Author NameUniversity of AuthorFaculty of Author
Abstract (2. Language): 
Proliferation capacity of normal somatic cells are limited. The most important reason of it is the fact that, the structure called telomere which is consist of DNA repetition, gets shorter in every cell cycle and it limits cell replication. Telomeres are formed of many repetition of hexanucleotide series (TTAGGG),, Mentioned hexanucleotides are located on the end of eukaryotic lineer chromosomes and they have no protein code. Morevcr, telomeres accompanied by many forms of specific proteins are necessary in order to prevent undesired effects such as edge-fusions and nucleotic effects, and it is also necessary in order to preserve genomic integrity. Cells with limited replication capacity enters in replicativc ageing through shortening of telomeres in every consecutive cell division. These proliferatively incapacitated cells in the stage of irreversible ageing arc metabolically active. It is reported that, in various diseases, age is the most important risk factor and there is a relation between the length of telomere and diseases depend on ageing. The preservation of telomere length and its stability is provided by "telomerase enzyme complex" which has its own RNA and proteins. In human cells, while telomerase enzyme activity is observed every region of body in first weeks of embryo, after that in most of the cells, the telomerase activity decreases depending on age factor. In time, some cells proliferate indefinably after telomerase enzyme regulation or reactivation. Cancer cells are this type of cells. Telomere shortening is considered to be an effective tumor suprcssor mechanism.
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Abstract (Original Language): 
Normal somatik hücrelerin proliferasyon kapasiteleri sınırlıdır. Bunun en önemli nedeni telomer adı verilen DNA tekrarlarından oluşan yapının her hücre siklusunda giderek kısalması ve hücre replikasyonunu sınırlandırmasıdır. Telomerler, ökaryotik lineer kromozomların uç bölgelerinde yer alan. protein kodu içermeyen, çok sayıda hekzonükleotid tekrar dizinlerinden (TTAGGG),, oluşur. Aynı zamanda birçok özelleşmiş proteinin eşlik ettiği telomerler, kromozomların uç füzyonlan ve nükleotik etkiler gibi istenmeyen etkilere karşı korunması ve genomik bütünlüğün sağlanması için gereklidir. Replikasyon kapasiteleri sınırlı olan hücreler, her bir ardışık hücre bölünmesiyle telomerlerin aşamalı olarak kısalması sonucu replikatif yaşlanmaya girerler. Bu geri dönüşümü olmayan replikatif yaşlanma evresindeki hücreler çoğalma kapasiteleri olmayan fakat metabolik olarak aktif hücrelerdir. Çeşitli hastalıklarda yaşın en büyük risk faktörü olduğu, yaşlanmaya bağlı olan kimi hastalıklarla telomer uzunluğu arasında bir ilişki bulunduğu belirtilmiştir. Telomer uzunluğunun korunmasını ve stabil kalmasını kendine ait bir RNA ve proteinleri bulunan 'telomeraz enzim kompleksi' sağlar. İnsan hücrelerinde telomeraz enzim işlevi embriyonun ilk haftaları boyunca hemen her yerde görülürken, daha sonra hücrelerin çoğunda yaşa bağlı olarak azalır. Zamanla bazı hücreler telomeraz enzim regülasyonu ya da yeniden aktifleşmesi sonucu belirsiz bir şekilde çoğalır. Kanser hücreleri bu tip hücrelerdir. Telomer kısalması etkili bir tümör supressor mekanizması olarak düşünülmektedir.
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İlker BOLAT. Nurullah KEKLİKOGLU. Sevtap İNCE AKINCI
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