The Drosophila U7 snRNP proteins Lsm10 and Lsm11 are required for histone pre-mRNA processing and play an essential role in development
The Drosophila U7 snRNP proteins Lsm10 and Lsm11 are required for histone pre-mRNA processing and play an essential role in development
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DOI：
10.1261/rna.1518009
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发表时间：
2009-09-01
期刊：
影响因子：
4.5
通讯作者：
Duronio, Robert J.
中科院分区：
文献类型：
--
作者：
Godfrey, Ashley C.;White, Anne E.;Duronio, Robert J.
依赖于后生动物复制的组蛋白mRNAs不是多腺化的，而是在保守的茎环结构中终止，该结构是由涉及U7 SnRNP的前-mRNA的内切作用产生的。U7SnRNP包含两个类Sm蛋白，Lsm10和Lsm11，它们取代了与剪接体SnRNAs结合的标准七聚体Sm蛋白环中的SmD1和SmD2。在这里，我们表明，果蝇Lsm10或Lsm11基因的突变扰乱了正常的组蛋白前mRNA加工，导致聚(A)+组蛋白mRNA的产生，这是转录通读到每个组蛋白基因下游存在的隐蔽的聚腺苷酸化位点的结果。这种分子表型与我们之前描述的U7SnRNA突变没有什么区别。Lsm10蛋白在Lsm11突变体中未能积聚，表明Lsm10-Lsm11二聚体为U7 SnRNP组装提供了前体。出人意料的是，在Lsm11和Lsm1突变体中检测到U7 SnRNA，并可与抗三甲基鸟苷抗体沉淀，这表明在没有Lsm10和Lsm11的情况下，它组装成SnRNP颗粒。然而，在组蛋白基因座体上没有检测到这种U7SnRNA，这表明Lsm10和Lsm11是U7SnRNP定位所必需的。与U7SnRNA缺失突变体相比，Lsm10和Lsm11突变体不能存活到成年。由于我们无法检测到Lsm10或Lsm11与U7突变体之间组蛋白mRNA表型的差异，我们认为不同的末端发育表型是由于Lsm10和Lsm11参与了一种不同于组蛋白前mRNA加工的基本功能，该功能独立于U7 SnRNA。
Metazoan replication-dependent histone mRNAs are not polyadenylated, and instead terminate in a conserved stem-loop structure generated by an endonucleolytic cleavage of the pre-mRNA involving U7 snRNP. U7 snRNP contains two like-Sm proteins, Lsm10 and Lsm11, which replace SmD1 and SmD2 in the canonical heptameric Sm protein ring that binds spliceosomal snRNAs. Here we show that mutations in either the Drosophila Lsm10 or the Lsm11 gene disrupt normal histone pre-mRNA processing, resulting in production of poly(A)+ histone mRNA as a result of transcriptional read-through to cryptic polyadenylation sites present downstream from each histone gene. This molecular phenotype is indistinguishable from that which we previously described for mutations in U7 snRNA. Lsm10 protein fails to accumulate in Lsm11 mutants, suggesting that a pool of Lsm10-Lsm11 dimers provides precursors for U7 snRNP assembly. Unexpectedly, U7 snRNA was detected in Lsm11 and Lsm1 mutants and could be precipitated with anti-trimethylguanosine antibodies, suggesting that it assembles into a snRNP particle in the absence of Lsm10 and Lsm11. However, this U7 snRNA could not be detected at the histone locus body, suggesting that Lsm10 and Lsm11 are necessary for U7 snRNP localization. In contrast to U7 snRNA null mutants, which are viable, Lsm10 and Lsm11 mutants do not survive to adulthood. Because we cannot detect differences in the histone mRNA phenotype between Lsm10 or Lsm11 and U7 mutants, we propose that the different terminal developmental phenotypes result from the participation of Lsm10 and Lsm11 in an essential function that is distinct from histone pre-mRNA processing and that is independent of U7 snRNA.