The C-terminal extension of Lsm4 interacts directly with the 3' end of the histone mRNP and is required for efficient histone mRNA degradation.
The C-terminal extension of Lsm4 interacts directly with the 3' end of the histone mRNP and is required for efficient histone mRNA degradation.
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DOI：
10.1261/rna.042531.113
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发表时间：
2014-01
期刊：
影响因子：
--
通讯作者：
Marzluff WF
中科院分区：
文献类型：
--
作者：
Lyons SM;Ricciardi AS;Guo AY;Kambach C;Marzluff WF
Lsm1-7环是组蛋白mRNA快速降解所必需的，并与组蛋白mRNA 3 '端的寡核苷酸(U)尾部结合。本文发现Lsm4的c端尾部与组蛋白mRNA 3′端结合的两个蛋白SLBP和3′hexo直接相互作用。不能结合组蛋白mRNP的突变体Lsm4蛋白稳定表达，并被纳入Lsm1-7环。表达这些蛋白的细胞不能迅速降解组蛋白mrna。Lsm1-7环可能通过直接与特定mRNA相互作用而被募集到许多mRNA靶标上。后生动物复制依赖性组蛋白mrna是唯一已知的真核生物中缺乏多聚(a)尾部的mrna，而是以保守的茎环序列结束，该序列与组蛋白mRNP上的茎环结合蛋白（SLBP）结合。哺乳动物细胞在S期DNA合成受到抑制时，组蛋白mrna迅速降解。组蛋白mrna的快速降解是由组蛋白mrna 3 '端的低尿嘧啶化引发的，需要细胞质Lsm1-7复合物，该复合物可以结合到寡核苷酸(U)尾部。外切酶3'hExo与SLBP和茎环形成三元复合物，是组蛋白mRNA降解起始所必需的。Lsm1-7复合体也参与聚腺苷化mrna的降解。它与死基化后剩余的寡核苷酸(A)尾部结合，抑制翻译并募集脱帽所需的酶。Lsm1-7复合物是否直接与mRNP的其他组分相互作用尚不清楚。我们在这里报道了Lsm4的c端延伸直接与组蛋白mRNP相互作用，与SLBP和3'hExo都有联系。当DNA合成受到抑制时，Lsm4 c端尾部阻止SLBP和3'hExo结合的突变体降低了组蛋白mRNA的降解率。
The Lsm1-7 ring is required for rapid histone mRNA degradation and binds to the oligo(U) tail added to the 3′ end of histone mRNA. This paper shows that the C-terminal tail of Lsm4 directly interacts with two proteins, SLBP and 3′hExo, bound to the 3′ end of histone mRNA. Mutant Lsm4 proteins that cannot bind the histone mRNP were stably expressed and were incorporated into the Lsm1-7 ring. Cells expressing these proteins do not degrade histone mRNAs rapidly. It is possible that the Lsm1-7 ring may be recruited to a number of mRNA targets by directly interacting with specific mRNPs. Metazoan replication-dependent histone mRNAs are the only known eukaryotic mRNAs that lack a poly(A) tail, ending instead in a conserved stem–loop sequence, which is bound to the stem–loop binding protein (SLBP) on the histone mRNP. Histone mRNAs are rapidly degraded when DNA synthesis is inhibited in S phase in mammalian cells. Rapid degradation of histone mRNAs is initiated by oligouridylation of the 3′ end of histone mRNAs and requires the cytoplasmic Lsm1-7 complex, which can bind to the oligo(U) tail. An exonuclease, 3′hExo, forms a ternary complex with SLBP and the stem–loop and is required for the initiation of histone mRNA degradation. The Lsm1-7 complex is also involved in degradation of polyadenylated mRNAs. It binds to the oligo(A) tail remaining after deadenylation, inhibiting translation and recruiting the enzymes required for decapping. Whether the Lsm1-7 complex interacts directly with other components of the mRNP is not known. We report here that the C-terminal extension of Lsm4 interacts directly with the histone mRNP, contacting both SLBP and 3′hExo. Mutants in the C-terminal tail of Lsm4 that prevent SLBP and 3′hExo binding reduce the rate of histone mRNA degradation when DNA synthesis is inhibited.
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