Estévez A M, Kempf T, Clayton C
Zentrum für Molekulare Biologie, Heidelberg Universität, Im Neuenheimer Feld 282, 69120-Heidelberg, Germany.
EMBO J. 2001 Jul 16;20(14):3831-9. doi: 10.1093/emboj/20.14.3831.
The yeast exosome is a complex of at least 10 essential 3'-5' riboexonucleases which is involved in 3'-processing of many RNA species. An exosome-like complex has been found or predicted to exist in other eukaryotes but not in Escherichia coli. The unicellular parasite Trypanosoma brucei diverged very early in eukaryotic evolution. We show here that T.brucei contains at least eight exosome subunit homologs, but only a subset of these associate in a complex. Accordingly, the T.brucei exosome is smaller than that of yeast. Both free and complex-associated homologs are essential for cell viability and are involved in 5.8S rRNA maturation. We suggest that the exosome was present in primitive eukaryotes, and became increasingly complex during subsequent evolution.
酵母外切体是一种由至少10种必需的3'-5'核糖核酸外切酶组成的复合物，参与多种RNA的3'端加工。在其他真核生物中已发现或预测存在类似外切体的复合物，但在大肠杆菌中不存在。单细胞寄生虫布氏锥虫在真核生物进化过程中分歧很早。我们在此表明，布氏锥虫含有至少8种外切体亚基同源物，但其中只有一部分会形成复合物。因此，布氏锥虫的外切体比酵母的小。游离的和与复合物相关的同源物对细胞活力都是必需的，并且参与5.8S rRNA的成熟。我们认为外切体存在于原始真核生物中，并在随后的进化过程中变得越来越复杂。
