Shpiz S G, Kalmykova A I
Institute of Molecular Genetics, Russian Academy of Sciences, Moscow 123182, Russia.
Biochemistry (Mosc). 2007 Jun;72(6):618-30. doi: 10.1134/s0006297907060041.
The telomeric nucleoprotein complex protects linear chromosome ends from degradation. In contrast to most eukaryotes in which telomerase is responsible for telomere elongation by adding short DNA repeats synthesized using an RNA template, the telomere elongation in Drosophila involves transposition of specialized telomeric retroelements onto chromosome ends. Proteins that bind telomeric and subtelomeric sequences form specific telomeric chromatin, and its components are highly conserved among organisms employing different mechanisms of telomere elongation. This review is focused on the analysis of components of the Drosophila telomeric complex and its comparison with telomeric proteins in telomerase-encoded organisms. Structural and functional analysis of Drosophila telomeres suggests that there are three distinct chromatin regions: protective structure at the very end of chromosome (cap), subtelomeric region which is characterized by condensed chromatin structure, and the terminal retrotransposon array whose expression is under the control of an RNAi (RNA interference)-based mechanism. The link between RNAi and telomeric chromatin formation in germinal tissues is discussed.
端粒核蛋白复合体保护线性染色体末端不被降解。与大多数真核生物不同，在这些真核生物中，端粒酶通过添加使用RNA模板合成的短DNA重复序列来负责端粒延长，而果蝇中的端粒延长涉及特殊端粒逆转座子转座到染色体末端。结合端粒和亚端粒序列的蛋白质形成特定的端粒染色质，并且在采用不同端粒延长机制的生物体中其组成成分高度保守。本综述聚焦于果蝇端粒复合体成分的分析及其与端粒酶编码生物体中端粒蛋白的比较。果蝇端粒的结构和功能分析表明存在三个不同的染色质区域：染色体最末端的保护结构（帽）、以浓缩染色质结构为特征的亚端粒区域以及其表达受基于RNA干扰（RNAi）机制控制的末端逆转座子阵列。本文还讨论了RNAi与生殖组织中端粒染色质形成之间的联系。
