18S nonfunctional rRNA decay
Nonfunctional rRNA decay (NRD) is a quality control mechanism system capable of detecting and eliminating translationally defective rRNAs.
NRD can be divided into two pathways:
1) 18S NRD - eliminates rRNAs with deleterious mutations in the decoding site
2) 25S NRD - eliminates rRNAs containing deleterious mutations in the peptidyl transferase center
18S NRD is dependent on translation elongation and utilizes the same proteins as those participating in no-go mRNA decay (NGD).
The key 18S RND participants are:
the major cytoplasmic 5'-3' exonuclease Xrn1p
the cytoplasmic exosome recruitment factor Ski7p
eRF3-like protein Hbs1p
eRF1-like protein Dom34p
Given all the similarities between 18S NRD and NGD, it is likely that what is being recognized in both cases is a ribosome inappropriately stalled on an mRNA due to an inability to elongate. In the case of 18S NRD, this stalling is due to a defect in the decoding center of the small ribosomal subunit, whereas in the case of
NGD, it is due to some structural barrier in the mRNA that prevents ribosome translocation. In both cases, the stalled ribsome contains a sense codon within the A-site. (PMID: 19481524)
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Last modification of this entry: July 12, 2012.