Pardue Mary-Lou, DeBaryshe P G
Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Annu Rev Genet. 2003;37:485-511. doi: 10.1146/annurev.genet.38.072902.093115.
Telomere molecular biology is far more complex than originally thought. Understanding biological systems is aided by study of evolutionary variants, and Drosophila telomeres are remarkable variants. Drosophila lack telomerase and the arrays of simple repeats generated by telomerase in almost all other organisms; instead, Drosophila telomeres are long tandem arrays of two non-LTR retrotransposons, HeT-A and TART. These are the first transposable elements found to have a bona fide role in cell structure, revealing an unexpected link between telomeres and what is generally considered to be parasitic DNA. In addition to providing insight into the cellular functions performed by telomeres, analysis of HeT-A and TART is providing insight into the evolution of chromosomes, retrotransposons, and retroviruses. Recent studies show that retrotransposon telomeres constitute a robust system for maintaining chromosome ends. These telomeres are now known to predate the separation of extant Drosophila species, allowing ample time for elements and hosts to coevolve interesting mechanisms.
端粒分子生物学远比最初想象的复杂。对进化变体的研究有助于理解生物系统，而果蝇端粒就是显著的变体。果蝇缺乏端粒酶以及几乎所有其他生物中端粒酶所产生的简单重复序列阵列；相反，果蝇端粒是由两个非长末端重复（non-LTR）逆转座子HeT-A和TART组成的长串联阵列。这些是首批被发现对细胞结构具有真正作用的转座元件，揭示了端粒与通常被认为是寄生性DNA之间意想不到的联系。除了有助于深入了解端粒所执行的细胞功能外，对HeT-A和TART的分析还为深入了解染色体、逆转座子和逆转录病毒的进化提供了线索。最近的研究表明，逆转座子端粒构成了一个用于维持染色体末端的强大系统。现在已知这些端粒早于现存果蝇物种的分化，这使得元件和宿主有足够的时间共同进化出有趣的机制。
