Maturation of the E. coli Glu2, Ile1, and Ala1B tRNAs utilizes a complex processing pathway,Molecular Microbiology

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Maturation of the E. coli Glu2, Ile1, and Ala1B tRNAs utilizes a complex processing pathway
Molecular Microbiology ( IF 2.6 ) Pub Date : 2022-06-02 , DOI: 10.1111/mmi.14949
Bijoy K Mohanty ₁ , Keri Nichols ₁ , Sidney R Kushner ₁

Affiliation

Despite significant progress in understanding the diversity of tRNA processing pathways in Escherichia coli, the mechanism for the maturation of tRNAs encoded within the rRNA operons has not received much attention. Here, we show that the Glu2, Ile1, and Ala1B tRNAs, encoded by 10 genes located between the 16S and 23S rRNAs in the seven rRNA operons, are matured via a RNase E-independent processing pathway that utilizes at least six different enzymes. It has been shown that the Glu2 and Ile1-Ala1B pre-tRNAs released by initial RNase III cleavages of the 30S primary rRNA transcripts retain extended 5′-leader (35–139 nt) and 3′-trailer (166–185 nt) sequences. However, the 5′ maturation of the tRNAs by RNase P is inhibited until the trailer sequences are shortened to 1–4 nucleotides, initially by a second RNase III cleavage at 31–42 nucleotides downstream of the CCA determinant followed by exonucleolytic trimming. The RNase III cleaved Glu2 and Ile1-Ala1B trailer fragments are degraded via PAP I- dependent exonucleolytic decay. Compared to the six previously characterized tRNA processing pathways, maturation of the Glu2, Ile1, and Ala1B tRNAs is considerably more complex and appears to be distinct from what occurs in Gram-positive bacteria.

中文翻译：

大肠杆菌 Glu2、Ile1 和 Ala1B tRNA 的成熟利用了复杂的加工途径

尽管在理解大肠杆菌中tRNA 加工途径的多样性方面取得了重大进展，在 rRNA 操纵子内编码的 tRNA 的成熟机制并未受到太多关注。在这里，我们展示了 Glu2、Ile1 和 Ala1B tRNA，由位于 7 个 rRNA 操纵子中 16S 和 23S rRNA 之间的 10 个基因编码，通过利用至少六种不同酶的不依赖 RNase E 的加工途径成熟。已经表明，由 30S 初级 rRNA 转录物的初始 RNase III 切割释放的 Glu2 和 Ile1-Ala1B 前 tRNA 保留了扩展的 5'-前导 (35-139 nt) 和 3'-拖尾 (166-185 nt) 序列. 然而，RNase P 对 tRNA 的 5' 成熟度受到抑制，直到尾部序列缩短为 1-4 个核苷酸，最初是通过在 CCA 决定簇下游 31-42 个核苷酸处进行第二次 RNase III 切割，然后进行核酸外切修剪。RNase III 切割的 Glu2 和 Ile1-Ala1B 尾随片段通过 PAP I 依赖性外切核酸降解降解。与先前表征的六种 tRNA 加工途径相比，Glu2、Ile1 和 Ala1B tRNA 的成熟要复杂得多，并且似乎与革兰氏阳性细菌中发生的情况不同。

更新日期：2022-06-02

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