MRNA去帽
mRNA去帽（mRNA decapping）又稱mRNA脫帽，是細胞中將mRNA的5′端帽水解還原成5′磷酸基的反應。真核生物細胞中正活躍轉譯的mRNA會與多核糖體結合，5′端帽會與eIF4E、eIF4G等起始因子結合而難與去帽酶接觸，在養分缺乏或受病毒感染等逆境中mRNA的轉譯可能被抑制，使5′端帽裸露，DCP2等去帽酶可將其5′端帽移除，之後mRNA的5′磷酸基會被RNA外切酶Xrn1等識別，使mRNA被快速降解[1][2] 。去帽與mRNA降解可能皆是在處理小體（P-body）中進行[3]。原核生物中也有類似機制，mRNA的5′端帽則可被RppH等去帽酶水解，將三磷酸基轉為單磷酸基，促進RNA被降解[4][5]。
真核生物中具無義突變的mRNA轉譯時會觸發无义介导的mRNA降解（NMD）途徑，將mRNA去帽後降解[6]。一些miRNA也可促進去帽酶與其目標的mRNA結合，進而將其去帽降解[7]。
參考文獻
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- ^ Hsieh, Ping-kun; Richards, Jamie; Liu, Quansheng; Belasco, Joel G. Specificity of RppH-dependent RNA degradation in Bacillus subtilis. Proceedings of the National Academy of Sciences. 22 April 2013, 110 (22): 8864–8869. PMC 3670361 . PMID 23610425. doi:10.1073/pnas.1222670110.
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- ^ Nishihara T, Zekri L, Braun JE, Izaurralde E. miRISC recruits decapping factors to miRNA targets to enhance their degradation.. Nucleic Acids Res. 2013, 41 (18): 8692–705. PMC 3794582 . PMID 23863838. doi:10.1093/nar/gkt619.