![syntorial no decay syntorial no decay](https://us-east-1.tchyn.io/snopes-production/uploads/2016/10/reverse-cavities-FI.jpg)
NGD thus plays a key role in resolving translational issues potentially detrimental to cellular homeostasis. NSD-targeted mRNAs are cleaved by an uncharacterized mechanism and become targets of NGD when ribosomes reach the new 3′-end and stall 9, 11, 12. For instance, transcripts synthesized without a stop codon due to premature polyadenylation have stalled ribosomes that are initially detected by the non-stop decay (NSD) pathway 9, 10.
![syntorial no decay syntorial no decay](https://kevinhunt.com.au/wp-content/uploads/2016/10/c5v20-mw-mic2-decay.jpg)
Other mRNA surveillance pathways can also ultimately lead to NGD. This mRNA degradation process is dependent on translation and involves an endoribonuclease that cleaves just upstream of the stall sequence 1, 5, 6, 9. NGD occurs when translation elongation is blocked by the presence of stable intramolecular or intermolecular RNA structures, enzymatic cleavage, chemically damaged sequences or rare codons 1, 3, 4, 5, 6, 7, 8. The No-Go Decay (NGD) mRNA surveillance pathway degrades mRNAs containing stalled ribosomes 1, 2. Finally, we identify the RNA kinase Trl1, alias Rlg1, as an essential player in the degradation of NGD RNAs. These cleavages map precisely in the mRNA exit tunnel of the ribosome, 8 nucleotides upstream of the first P-site residue and release 5′-hydroxylated RNA fragments requiring 5′-phosphorylation prior to digestion by the exoribonuclease Xrn1, or alternatively by Dxo1. This technique allows us to analyse endonucleolytic cleavage events at single-nucleotide resolution starting at the third collided ribosome, which we show to be Hel2-dependent. Here we use mRNAs expressing a 3′-ribozyme to produce truncated transcripts in vivo to mimic naturally occurring truncated mRNAs known to trigger NGD. Although an endoribonuclease has been proposed to initiate cleavages upstream of the stall sequence, the production of two RNA fragments resulting from a unique cleavage has never been demonstrated. The No-Go Decay (NGD) mRNA surveillance pathway degrades mRNAs containing stacks of stalled ribosomes.