A complex pathway for 3′ processing of the yeast U3 snoRNA
A complex pathway for 3′ processing of the yeast U3 snoRNA
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DOI：
10.1093/nar/gkg904
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发表时间：
2003-12-01
影响因子：
14.9
通讯作者：
Tollervey, D
中科院分区：
文献类型：
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作者：
Kufel, J;Allmang, C;Tollervey, D
酵母中成熟的U3 snoRNA是由3‘-延伸的前体通过内切和核外切割产生的。这些前体终止于聚(U)链，通常通过酵母La同系物Lhp1p的结合而稳定。我们报告说，U3的正常3‘加工需要核LSM蛋白。当五种必需蛋白质Lsm2-5p或Lsm8p中的任何一种被耗尽时，U3 snoRNA的正常3‘-延伸前体就会丢失。在LSM缺失的菌株中，成熟和前U3的截短片段都积累起来，与实质性的RNA降解一致。Pre-U3与TAP标记的Lsm3p共沉淀，但在缺乏Lhp1p的菌株中，与剪接的Pre-U3失去关联。当Lsm3p或Lsm5p缺失时，Lhp1p与Pre-U3的结合也减少，表明Lhp1p与LSM蛋白的结合是相互依赖的。相反，标记的Sm蛋白仅在缺乏Lhp1p的菌株中可检测到共沉淀剪接的Pre-U3物种。我们认为Lsm2-8p复合体作为伴侣与Lhp1p一起在3‘加工过程中稳定U3前RNA物种。Sm复合体可以起到稳定不受Lhp1p保护的3‘端的后备作用。
Mature U3 snoRNA in yeast is generated from the 3'-extended precursors by endonucleolytic cleavage followed by exonucleolytic trimming. These precursors terminate in poly(U) tracts and are normally stabilised by binding of the yeast La homologue, Lhp1p. We report that normal 3' processing of U3 requires the nuclear Lsm proteins. On depletion of any of the five essential proteins, Lsm2-5p or Lsm8p, the normal 3'-extended precursors to the U3 snoRNA were lost. Truncated fragments of both mature and pre-U3 accumulated in the Lsm-depleted strains, consistent with substantial RNA degradation. Pre-U3 species were co-precipitated with TAP-tagged Lsm3p, but the association with spliced pre-U3 was lost in strains lacking Lhp1p. The association of Lhp1p with pre-U3 was also reduced on depletion of Lsm3p or Lsm5p, indicating that binding of Lhp1p and the Lsm proteins is interdependent. In contrast, a tagged Sm-protein detectably co-precipitated spliced pre-U3 species only in strains lacking Lhp1p. We propose that the Lsm2-8p complex functions as a chaperone in conjunction with Lhp1p to stabilise pre-U3 RNA species during 3' processing. The Sm complex may function as a back-up to stabilise 3' ends that are not protected by Lhp1p.