Yamada O
Department of Hematology, Tokyo Women's Medical College, Japan.
Int J Hematol. 1996 Aug;64(2):87-99. doi: 10.1016/0925-5710(96)00473-2.
Telomeres are the physical ends of eukaryotic chromosomes. Telomeric DNA sequences are highly conserved in all well-characterized eukaryotic nuclear chromosomes and differ greatly from the termini of linear viral, extranuclear plasmid, or mitochondrial DNA. Human telomeric DNA consists of 2-15 kb of a tandemly repeated sequence (TTAGGG)n, oriented 5'-3' toward the end of the chromosome. The evolutionary conservation of this repetitive DNA sequence implies that the sequence is essential to cellular function. These repeated sequences are synthesized by an RNA-dependent DNA polymerase, telomerase, which is composed of an essential RNA and a few proteins. Human telomerase has been proposed to be repressed in somatic tissues, and human telomeres become shorter during somatic development and with increasing age. Telomeres in tumors are even shorter, and loss of telomeric DNA during tumorigenesis may contribute to the genome instability associated with transformed cells. This article reviews the structure and function of telomeres and the recent studies on human hematologic cells.
端粒是真核生物染色体的物理末端。端粒DNA序列在所有特征明确的真核细胞核染色体中高度保守，与线性病毒、核外质粒或线粒体DNA的末端有很大不同。人类端粒DNA由2 - 15 kb的串联重复序列(TTAGGG)n组成，其5'-3'方向朝向染色体末端。这种重复DNA序列的进化保守性意味着该序列对细胞功能至关重要。这些重复序列由一种RNA依赖性DNA聚合酶——端粒酶合成，端粒酶由一种必需的RNA和一些蛋白质组成。有人提出人类端粒酶在体细胞组织中受到抑制，并且人类端粒在体细胞发育过程中以及随着年龄增长会变短。肿瘤中的端粒甚至更短，肿瘤发生过程中端粒DNA的丢失可能导致与转化细胞相关的基因组不稳定。本文综述了端粒的结构和功能以及近期关于人类血细胞的研究。
