Nonsense-mediated mRNA decay in mammalian cells involves decapping, deadenylating, and exonucleolytic activities
Nonsense-mediated mRNA decay in mammalian cells involves decapping, deadenylating, and exonucleolytic activities
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DOI：
10.1016/s1097-2765(03)00349-6
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发表时间：
2003-09-01
期刊：
影响因子：
16
通讯作者：
Maquat, LE
中科院分区：
文献类型：
--
作者：
Lejeune, F;Li, XJ;Maquat, LE
无意义介导的信使核糖核酸衰退(NMD)是细胞识别和降解过早终止翻译的信使核糖核酸的一种机制。到目前为止，哺乳动物细胞中NMD的极性和酶学还不清楚。我们在这里表明，下调外体的Dcp2解帽蛋白或PM/Scl100成分(1)显著增加含有无义但不含无义的稳态mRNAs的丰度，以及(2)显著减缓瞬时诱导的含有无义但不含无义的mRNAs的衰减速度。下调聚(A)核糖核酸酶(PARN)也会增加含有废话的mRNAs的丰度。此外，NMD因子UPF1、Upf2和Upf3X与解帽酶Dcp2、推测的5‘-gt；3’外切酶Rat1、已证实的5‘-gt；3’外切酶Xrn1、外体成分PM/Scl100、Rrp4和Rrp41以及Parn共免疫纯化。根据这些和其他数据，我们得出结论，哺乳动物细胞中的NMD通过招募解帽和5‘-gt；3’外切酶活性以及去烯化和3‘-gt；5’外核酸酶活性来降解来自5‘和3’端的mRNAs。
Nonsense-mediated mRNA decay (NMD) is a mechanism by which cells recognize and degrade mRNAs that prematurely terminate translation. To date, the polarity and enzymology of NMD in mammalian cells is unknown. We show here that downregulating the Dcp2 decapping protein or the PM/Scl100 component of the exosome (1) significantly increases the abundance of steady-state nonsense-containing but not nonsense-free mRNAs, and (2) significantly slows the decay rate of transiently induced nonsense-containing but not nonsense-free mRNA. Downregulating poly(A) ribonuclease (PARN) also increases the abundance of nonsense-containing mRNAs. Furthermore, NMD factors Upf1, Upf2, and Upf3X coimmunopurify with the decapping enzyme Dcp2, the putative 5'-->3' exonuclease Rat1, the proven 5'-->3' exonuclease Xrn1, exosomal components PM/Scl100, Rrp4, and Rrp41, and PARN. From these and other data, we conclude that NMD in mammalian cells degrades mRNAs from both 5' and 3' ends by recruiting decapping and 5'-->3' exonuclease activities as well as deadenylating and 3'-->5' exonuclease activities.