Wai Lin Kah
Lviv National Medical University, Lviv, Ukraine.
MedGenMed. 2004 Jul 26;6(3):19.
Human telomeres function as a protective structure capping both ends of the chromosome. They are composed of long, repetitive sequences of TTAGGG, associated with a variety of telomere-binding proteins. Telomeres protect the chromosomes from end-to-end fusion, recombination, and degradation, all events that can lead to cell death. At cell replication, telomeres cannot be completely replicated. They are gradually shortened, and when the telomeres reach a critical threshold, cell replication is arrested in what is called "replicative senescence." Thus, telomeres act as an intrinsic "counting" mechanism of the cell's aging process. Telomerase is an enzymatic ribonucleoprotein complex that acts as a reverse transcriptase in the elongation of telomeres. Telomerase activity is almost absent in somatic cells, but it is detected in embryonic stem cells and in the vast majority of tumor cells. Tumor cells, in fact, may contain short and stable telomeres that confer immortality to the cancer cells, which are thus able to replicate indefinitely. The deregulation of telomeres thus plays an important role in the relationship between premature aging syndrome and cancer. This review describes the recent advances in the molecular characterization of telomeres, the regulation of telomerase
人类端粒作为一种保护结构覆盖在染色体的两端。它们由TTAGGG的长重复序列组成，并与多种端粒结合蛋白相关联。端粒保护染色体免受体端融合、重组和降解，这些事件均可导致细胞死亡。在细胞复制时，端粒无法完全复制。它们会逐渐缩短，当端粒达到临界阈值时，细胞复制会在所谓的“复制性衰老”中停止。因此，端粒充当细胞衰老过程的一种内在“计数”机制。端粒酶是一种酶促核糖核蛋白复合物，在端粒延长过程中作为逆转录酶发挥作用。端粒酶活性在体细胞中几乎不存在，但在胚胎干细胞和绝大多数肿瘤细胞中可检测到。事实上，肿瘤细胞可能含有短而稳定的端粒，赋予癌细胞永生性，使其能够无限复制。因此，端粒失调在早衰综合征与癌症的关系中起着重要作用。本综述描述了端粒分子特征、端粒酶调控方面的最新进展。
