Zentrum für Molekulare Biologie der Universität Heidelberg, DKFZ-ZMBH Alliance, D69120 Heidelberg, Germany.
RNA. 2013 Jul;19(7):937-47. doi: 10.1261/rna.038430.113. Epub 2013 May 22.
The degradation of eukaryotic mRNAs can be initiated by deadenylation, decapping, or endonuclease cleavage. This is followed by 5'-3' degradation by homologs of Xrn1, and/or 3'-5' degradation by the exosome. We previously reported that, in African trypanosome Trypanosoma brucei, most mRNAs are deadenylated prior to degradation, and that depletion of the major 5'-3' exoribonuclease XRNA preferentially stabilizes unstable mRNAs. We now show that depletion of either CAF1 or CNOT10, two components of the principal deadenylation complex, strongly inhibits degradation of most mRNAs. RNAi targeting another deadenylase, PAN2, or RRP45, a core component of the exosome, preferentially stabilized mRNAs with intermediate half-lives. RRP45 depletion resulted in a 5' bias of mRNA sequences, suggesting action by a distributive 3'-5' exoribonuclease. Results suggested that the exosome is involved in the processing of trypanosome snoRNAs. There was no correlation between effects on half-lives and on mRNA abundance.
真核 mRNA 的降解可以通过加尾、去帽或内切核酸酶切割来启动。随后，Xrn1 的同源物进行 5'-3'降解，外切体进行 3'-5'降解。我们之前曾报道，在非洲锥虫 Trypanosoma brucei 中，大多数 mRNA 在降解前都被加尾，主要的 5'-3'外切核酸酶 XRNA 的消耗优先稳定不稳定的 mRNA。我们现在表明，耗尽主要加尾复合物的两个成分 CAF1 或 CNOT10，强烈抑制大多数 mRNA 的降解。针对另一种加尾酶 PAN2 或外切体核心成分 RRP45 的 RNAi，优先稳定半衰期中等的 mRNA。RRP45 的消耗导致 mRNA 序列的 5'偏向，表明存在分布的 3'-5'外切核酸酶的作用。结果表明外切体参与了锥虫 snoRNA 的加工。半衰期和 mRNA 丰度的影响之间没有相关性。
