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#RNase D

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Processing of rRNA and tRNA

RNase D trims tRNA from

RNase D functions with strict 3' to 5' polarity, removing nucleotides from 3' end towards 5' direction. After RNase P and RNase E liberate pre-tRNA with extended 3' trailer, RNase D binds exposed 3' single strand and sequentially hydrolyzes phosphodiester bonds, advancing backward. Strong secondary structure and mature CCA end block further degradation, defining stopping point. This orientation protects upstream coding regions while achieving terminal precision needed for CCA addition and aminoacylation, maintaining tRNA integrity and turnover control. This refined regulation supports accurate

Ref: Lodish et al., Molecular Cell Biology, 9th ed., Chapter 8, Directionality of RNase D trimming at tRNA 3' end

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Processing of rRNA and tRNA

RNase D acts as

RNase D encoded by rnd gene in E. coli is hydrolytic 3' to 5' exonuclease requiring Mg2+ that digests single-stranded RNA from free 3' hydroxyl. It participates in final trimming of tRNA precursors, 5S rRNA, and other stable RNAs after initial endonucleolytic cuts. Unlike endonucleases RNase III, E and P which cut internally, RNase D nibbles one nucleotide at a time until stopped by stable secondary structure like acceptor stem. Its distributive action provides proofreading precision, preventing over-digestion and ensuring accurate mature ends.

Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 6, RNase D 3'-5' exonuclease family

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