Telomeres, tethers and trypanosomes
Telomeres, tethers and trypanosomes
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DOI：
10.4161/nucl.22167
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发表时间：
2012-11-01
期刊：
影响因子：
3.7
通讯作者：
Rout, Michael P.
中科院分区：
文献类型：
--
作者：
Field, Mark C.;Horn, David;Rout, Michael P.
细胞核的时空组织对于转录控制、mRNA加工以及核糖体组装至关重要。这包括哺乳动物染色体占据特定区域、核仁及卡哈尔体等亚核区室的存在，以及染色质在活性与非活性状态之间的划分。后一种情况通常分别与常染色质和异染色质内DNA的位置相关；关键的是，这些差异是通过对包括组蛋白在内的染色质相关蛋白的修饰以及异染色质在核周边的优先定位而产生的。大多数关于细胞核组织的研究都集中在后生动物和真菌上；然而，近期的技术进步使得对差异更大的真核生物进行研究成为可能，并取得了一些令人惊讶的结果。例如，在后生动物细胞核中，异染色质的组织在很大程度上是由核纤层蛋白介导的，核纤层蛋白是典型的中间丝蛋白。尽管在大多数真核生物中通过生化方法和电子显微镜都能检测到异染色质，但直到今年，人们还认为核纤层蛋白仅限于后生动物类群，而其他谱系中构成核纤层的蛋白质还不清楚。近期的研究表明变形虫中存在核纤层蛋白的同源物，而锥虫具有一种大的卷曲螺旋蛋白NUP - 1，其功能与核纤层蛋白类似。这些数据表明核纤层的存在比之前认为的要广泛得多，这对真核生物基因表达机制的进化具有重要意义。我们讨论了这些以及其他关于不同生物细胞核组织的近期发现，以及这些发现对真核生物进化起源的影响。
Temporal and spatial organization of the nucleus is critical for the control of transcription, mRNA processing and the assembly of ribosomes. This includes the occupancy of specific territories by mammalian chromosomes, the presence of subnuclear compartments such as the nucleolus and Cajal bodies and the division of chromatin between active and inactive states. These latter are commonly associated with the location of DNA within euchromatin and heterochromatin respectively; critically these distinctions arise through modifications to chromatin-associated proteins, including histones, as well as the preferential localization of heterochromatin at the nuclear periphery. Most research on nuclear organization has focused on metazoa and fungi; however, recent technical advances have made more divergent eukaryotes accessible to study, with some surprising results. For example, the organization of heterochromatin is mediated in metazoan nuclei in large part by lamins, the prototypical intermediate filament proteins. Despite the presence of heterochromatin, detected both biochemically and by EM in most eukaryotic organisms, until this year lamins were thought to be restricted to metazoan taxa, and the proteins comprising the lamina in other lineages were unknown. Recent work indicates the presence of lamin orthologs in amoeba, while try-panosomatids possess a large coiled-coil protein, NUP-1, that performs functions analogous to lamins. These data indicate that the presence of a nuclear lamina is substantially more widespread than previously thought, with major implications for the evolution of eukaryotic gene expression mechanisms. We discuss these and other recent findings on the organization of nuclei in diverse organisms, and the implications of these findings for the evolutionary origin of eukaryotes.