Houseley Jonathan, Tollervey David
Wellcome Trust Centre for Cell Biology, University of Edinburgh, Swann Building, King's Buildings, Edinburgh EH9 3JR, UK.
EMBO Rep. 2006 Feb;7(2):205-11. doi: 10.1038/sj.embor.7400612.
Recent analyses have shown that the activity of the yeast nuclear exosome is stimulated by the Trf4p-Air1/2p-Mtr4p polyadenylation (TRAMP) complex. Here, we report that strains lacking the Rrp6p component of the nuclear exosome accumulate polyadenylated forms of many different ribosomal RNA precursors (pre-rRNAs). This polyadenylation is reduced in strains lacking either the poly(A) polymerase Trf4p or its close homologue Trf5p. In contrast, polyadenylation is enhanced by overexpression of Trf5p. Polyadenylation is also markedly increased in strains lacking the RNA helicase Mtr4p, indicating that it is required to couple poly(A) polymerase activity to degradation. Tandem affinity purification-tagged purified Trf5p showed polyadenylation activity in vitro, which was abolished by a double point mutation in the predicted catalytic site. Trf5p co-purified with Mtr4p and Air1p, indicating that it forms a complex, designated TRAMP5, that has functions that partially overlap with the TRAMP complex.
最近的分析表明,酵母核外切体的活性受到Trf4p-Air1/2p-Mtr4p多聚腺苷酸化(TRAMP)复合体的刺激。在此,我们报告,缺乏核外切体Rrp6p组分的菌株积累了许多不同核糖体RNA前体(前体rRNA)的多聚腺苷酸化形式。在缺乏多聚腺苷酸聚合酶Trf4p或其紧密同源物Trf5p的菌株中,这种多聚腺苷酸化作用减弱。相反,Trf5p的过表达增强了多聚腺苷酸化作用。在缺乏RNA解旋酶Mtr4p的菌株中,多聚腺苷酸化也显著增加,表明它是将多聚腺苷酸聚合酶活性与降解偶联所必需的。串联亲和纯化标签纯化的Trf5p在体外显示出多聚腺苷酸化活性,该活性在预测的催化位点的双点突变后被消除。Trf5p与Mtr4p和Air1p共同纯化,表明它形成了一个复合体,命名为TRAMP5,其功能与TRAMP复合体部分重叠。