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转运-信使RNA

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维基百科,自由的百科全书
转运-信使RNA
tmRNA (PDB 3IYR)
识别符
代号 tmRNA
Rfam RF00023
其他数据
RNA类型 基因
tmRNA同時具有tRNA與mRNA的功能與結構

转运-信使RNA(Transfer-messenger RNA,簡稱tmRNA,舊稱10Sa RNASsr RNA)是細菌中一種同時具有mRNAtRNA功能與結構的RNA,此RNA本身如mRNA般具有編碼區,3'端可如tRNA般由丙胺酸-tRNA合成酶英语Alanine—tRNA ligase加上一個丙胺酸[1],長度多介於320至400nt之間(少數結構退化者可能更短)[2],當細胞中的核糖體轉譯mRNA發生停滯時(包括mRNA突變而失去終止密碼子等原因),tmRNA可與SmpB蛋白與EF-Tu等組合成一核糖核蛋白,並結合至核糖體空出的A位英语A-site以啟動反式轉譯(trans-translation),即將核糖體合成中的多肽轉移至其3'端的丙胺酸上,以tmRNA的編碼區為模板繼續轉譯數個胺基酸後再遇到終止密碼子而結束,轉譯出的蛋白末端帶有丙胺酸和tmRNA編碼的小段多肽序列(在大腸桿菌中為AANDENYALAA),此段序列通常會被細胞中的蛋白酶識別而將整個蛋白質降解[3],造成轉譯停滯的mRNA也會被水解移除[4]

幾乎所有細菌基因組中皆具有編碼tmRNA的基因[5],此RNA對某些細菌的生長相當重要,也有細菌在較為不利的生長條件下才需tmRNA[6]。tmRNA的合成途徑和tRNA相似,轉錄後其5'端有一段序列需由核糖核酸酶P切割[1],3'端也有些序列需由核糖核酸酶T英语Ribonuclease T核糖核酸酶PH英语RNase PH切除[7][8],可連接丙胺酸的3'-CCA序列在某些物種是由基因編碼,因此轉錄完成時即具備,某些物種則是在tmRNA轉錄與切割之後才由tRNA核苷酸转移酶英语tRNA nucleotidyltransferase加上[9]。另外α-變形菌、某些藍綠菌與少數β-變形菌的tmRNA是由兩段RNA組成的,其中一段RNA的3'端結合丙胺酸,另一段RNA則具編碼序列,兩者僅以鹼基配對的氫鍵相互結合[10]

tmRNA最早於1979年研究人員以電泳分析大腸桿菌RNA時與核糖核酸酶P上的M1RNA(舊稱10Sb RNA)一起被發現,當時被命名為10Sa RNA[11] ,後續研究發現10Sa RNA具有常見於tRNA的假尿嘧啶核苷,且其3'端與tRNA的結構相似[12]。1995年始發現tmRNA還有編碼蛋白序列的功能[13]。除細菌外,少數真核生物(雅各比蟲英语jakobid與屬卵菌大豆疫霉菌英语Phytophthora sojae粒線體中的mtDNA也有編碼tmRNA,但皆已失去與mRNA相似的編碼區,僅存與tRNA相似的區域[9],還有數種藻類的質粒體中具有tmRNA,結構簡化但仍具編碼區和tRNA相似區[14]

反式轉譯過程示意圖

參見

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參考文獻

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  1. ^ 1.0 1.1 Komine Y, Kitabatake M, Yokogawa T, Nishikawa K, Inokuchi H. A tRNA-like structure is present in 10Sa RNA, a small stable RNA from Escherichia coli. Proceedings of the National Academy of Sciences of the United States of America. September 1994, 91 (20): 9223–7. PMC 44784可免费查阅. PMID 7524073. doi:10.1073/pnas.91.20.9223. 
  2. ^ Janssen BD, Hayes CS. The tmRNA ribosome-rescue system.. Adv Protein Chem Struct Biol. 2012, 86: 151–91. PMC 3358797可免费查阅. PMID 22243584. doi:10.1016/B978-0-12-386497-0.00005-0. 
  3. ^ Keiler KC, Waller PR, Sauer RT. Role of a peptide tagging system in degradation of proteins synthesized from damaged messenger RNA. Science. 1996, 271 (5251): 990–3. PMID 8584937. doi:10.1126/science.271.5251.990. 
  4. ^ Keiler KC. Biology of trans-translation. Annual Review of Microbiology. 2008, 62: 133–51. PMID 18557701. doi:10.1146/annurev.micro.62.081307.162948. 
  5. ^ Schönhuber W, Le Bourhis G, Tremblay J, Amann R, Kulakauskas S. Utilization of tmRNA sequences for bacterial identification.. BMC Microbiol. 2001, 1: 20. PMC 55692可免费查阅. PMID 11560762. doi:10.1186/1471-2180-1-20. 
  6. ^ Thibonnier M, Thiberge JM, De Reuse H. Ahmed N , 编. Trans-translation in Helicobacter pylori: essentiality of ribosome rescue and requirement of protein tagging for stress resistance and competence. PLOS ONE. 2008, 3 (11): e3810. PMC 2584231可免费查阅. PMID 19043582. doi:10.1371/journal.pone.0003810. 
  7. ^ Srivastava RA, Srivastava N, Apirion D. Characterization of the RNA processing enzyme RNase III from wild type and overexpressing Escherichia coli cells in processing natural RNA substrates. The International Journal of Biochemistry. 1992, 24 (5): 737–49. PMID 1375563. doi:10.1016/0020-711X(92)90007-N. 
  8. ^ Li Z, Pandit S, Deutscher MP. 3' exoribonucleolytic trimming is a common feature of the maturation of small, stable RNAs in Escherichia coli. Proceedings of the National Academy of Sciences of the United States of America. 1998, 95 (6): 2856–61. PMC 19659可免费查阅. PMID 9501180. doi:10.1073/pnas.95.6.2856. 
  9. ^ 9.0 9.1 Hafez M, Burger G, Steinberg SV, Lang BF. A second eukaryotic group with mitochondrion-encoded tmRNA: in silico identification and experimental confirmation.. RNA Biol. 2013, 10 (7): 1117–24. PMC 3849159可免费查阅. PMID 23823571. doi:10.4161/rna.25376. 
  10. ^ Mao C, Bhardwaj K, Sharkady SM, Fish RI, Driscoll T, Wower J; et al. Variations on the tmRNA gene.. RNA Biol. 2009, 6 (4): 355–61. PMID 19617710. doi:10.4161/rna.6.4.9172. 
  11. ^ Ray BK, Apirion D. Characterization of 10S RNA: a new stable rna molecule from Escherichia coli. Molecular & General Genetics. 1979, 174 (1): 25–32. PMID 384159. doi:10.1007/BF00433301. 
  12. ^ Tyagi JS, Kinger AK. Identification of the 10Sa RNA structural gene of Mycobacterium tuberculosis. Nucleic Acids Research. 1992, 20 (1): 138. PMC 310338可免费查阅. PMID 1371186. doi:10.1093/nar/20.1.138. 
  13. ^ Tu GF, Reid GE, Zhang JG, Moritz RL, Simpson RJ. C-terminal extension of truncated recombinant proteins in Escherichia coli with a 10Sa RNA decapeptide. The Journal of Biological Chemistry. 1995, 270 (16): 9322–6. PMID 7536743. doi:10.1074/jbc.270.16.9322. 
  14. ^ Gueneau de Novoa P, Williams KP. The tmRNA website: reductive evolution of tmRNA in plastids and other endosymbionts.. Nucleic Acids Res. 2004, 32 (Database issue): D104–8. PMC 308836可免费查阅. PMID 14681369. doi:10.1093/nar/gkh102.