Non-stop decay

Non-stop decay is a cellular mechanism of mRNA surveillance to detect mRNA molecules lacking a stop codon and prevent these mRNAs from translation. The non-stop decay pathway releases ribosomes that have reached the far 3' end of an mRNA and guides the mRNA to the exosome complex, or to RNase R in bacteria for selective degradation.[1][2] In contrast to NMD, polypeptides do not release from the ribosome, and thus, NSD seems to involve mRNA decay factors distinct from NMD.[3]

Non-Stop Decay

Non-stop decay is a cellular pathway that identifies and degrades aberrant mRNA transcripts that do not contain a proper stop codons.[4] Stop codons are signals in messenger RNA that signal for synthesis of proteins to end.[5] Aberrant transcripts are identified during translation when the ribosome translates into the poly A tail at the 3' end of mRNA.[4] A non-stop transcript can occur when point mutations damage the normal stop codon. Moreover, some transcriptions are more likely to preserve low scale of gene expression in a particular state.[4]

The non-stop decay pathway discharges the ribosomes that have stalled at the 3' end of mRNA and directs the mRNA to the exosome complex in eukaryotes or RNase R in bacteria, where the transcript is then degraded.[2]

Liberation of the Ribosome

The trans-translation procedure is a bacterial mechanism to resolve stalled ribosomes.[2] It consists of the hybrid transfer RNA and messenger RNA (tm-RNA) with the small protein SmpB.[2] When the ribosome stalls at the 3'end of mRNA the tm-RNA is joined to the ribosome from the A site which has amino acid attached to it (11-amino acid tag).[6] Then, the amino acid binds to the polypeptide chain.[6] Then the normal translation will translate the tm-RNA codons sequence that will provide a particular tag which signifies that the protein is incomplete.[6] Ultimately, liberated that stalled ribosome.

mRNA Degradation

Many enzymes and proteins play role in degrading mRNA. For example, in Escherichia Coli there are three enzymes: RNase II, PNPase, and RNase R.[3] RNase R is a 3’-5’ exoribonuclease that recruited to degrade a defective mRNA.[6] RNase R has two distinct structural domains, N-terminal putative helix-turn-helix (HTH) and C-terminal lysine(K-rich) domains.[7] Evidence has been shown the role of K-rich domain in the degradation of non-stop mRNA.[7] These domains are not present in other RNases. Both RNases II and RNase R are members of RNR family, and they have a significant similarity in primary sequence and domain architecture.[2] However, RNase R has unique ability to degrade, while RNase II has less efficient in degrading. Nevertheless, the procedure of degrading mRNA via RNase R has remained anonymous.[6]

See also

References

  1. ↑ Vasudevan; Peltz, SW; Wilusz, CJ; et al. (2002). "Non-stop decay--a new mRNA surveillance pathway". BioEssays. 24 (9): 785–8. doi:10.1002/bies.10153. PMID 12210514.
  2. 1 2 3 4 5 Venkataraman, K; Guja, KE; Garcia-Diaz, M; Karzai, AW (2014). "Non-stop mRNA decay: a special attribute of trans-translation mediated ribosome rescue". Frontiers in Microbiology. 5: 93. doi:10.3389/fmicb.2014.00093. PMC 3949413. PMID 24653719.
  3. 1 2 Wu, X; Brewer, G (2012). "The regulation of mRNA stability in mammalian cells: 2.0". Gene. 500: 10–21. doi:10.1016/j.gene.2012.03.021. PMC 3340483. PMID 22452843.
  4. 1 2 3 Klauer, A. Alejandra; van Hoof, Ambro (2012-09-01). "Degradation of mRNAs that lack a stop codon: a decade of nonstop progress". Wiley Interdisciplinary Reviews: RNA. 3 (5): 649–660. doi:10.1002/wrna.1124. ISSN 1757-7012. PMC 3638749.
  5. ↑ Lewins genes XII. Jones and Bartlett Publishers: Jones & Bartlett Learning. 17 March 2017. ISBN 978-1284104493.
  6. 1 2 3 4 5 Alberts, Bruce (2002). Molecular biology of the cell 4th edition. New York: Garland Science. ISBN 0-8153-3218-1.
  7. 1 2 Vasudevan, Shobha; Peltz, Stuart W.; Wilusz, Carol J. (September 2002). "Non-stop decay--a new mRNA surveillance pathway". BioEssays: News and Reviews in Molecular, Cellular and Developmental Biology. 24 (9): 785–788. doi:10.1002/bies.10153. ISSN 0265-9247. PMID 12210514.
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