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'''Non-stop decay (NMD)''' is a [[Cell (biology)|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.<ref>{{cite journal
'''Non-stop decay (NSD)''' is a [[Cell (biology)|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.<ref>{{cite journal
|author=Vasudevan
|author=Vasudevan
|title=Non-stop decay--a new mRNA surveillance pathway
|title=Non-stop decay--a new mRNA surveillance pathway

Revision as of 10:28, 27 March 2019

Non-stop decay (NSD) 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 Nonsense-mediated decay (NMD), polypeptides do not release from the ribosome, and thus, NSD seems to involve mRNA decay factors distinct from NMD.[3]

Non-Stop Decay (NSD)

Non-stop decay (NSD) is a cellular pathway that identifies and degrades aberrant mRNA transcripts that do not contain a proper stop codon.[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 NSD 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] The NSD mechanism requires the interaction of RNA exosome with the Ski complex, a multi-protein structure that includes the Ski2p helicase and (notably) Ski7p; this combination activates the degradation of aberrant mRNAs.[6][7] Ski7p is thought to bind the ribosome stalled at the 3’ end of the mRNA poly(A) tail and recruit the exosome to degrade the aberrant mRNA. However in mammalian cells, Ski7p is not found, and even the presence of the NSD mechanism itself has remained enigmatic. The short splicing isoform of HBS1L (HBS1LV3) was found to be the long-sought human homologue of Ski7p linking the exosome and SKI complexes.[8] NSD was reported to occur in mammals, where the process was shown to depend on Hbs1, Dom34 (a binding partner of Hbs1), and components of the exosome-Ski complex (including, SKIV2L helicase, the human homolog of the yeast Ski2).[9]

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).[10] Then, the amino acid binds to the polypeptide chain.[10] Then the normal translation will translate the tm-RNA codons sequence that will provide a particular tag which signifies that the protein is incomplete.[10] 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.[10] RNase R has two distinct structural domains, N-terminal putative helix-turn-helix (HTH) and C-terminal lysine(K-rich) domains.[11] Evidence has been shown the role of K-rich domain in the degradation of non-stop mRNA.[11] 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 efficiency in degrading. Nevertheless, the procedure of degrading mRNA via RNase R has remained anonymous.[10]

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. ^ a b c d e 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.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  3. ^ a b Wu, X; Brewer, G (2012). "The regulation of mRNA stability in mammalian cells: 2.0". Gene. 500 (1): 10–21. doi:10.1016/j.gene.2012.03.021. PMC 3340483. PMID 22452843.
  4. ^ a b c 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. PMID 22740367.
  5. ^ Lewins genes XII. Jones and Bartlett Publishers: Jones & Bartlett Learning. 17 March 2017. ISBN 978-1284104493.
  6. ^ Lebreton, Alice; Tomecki, Rafal; Dziembowski, Andrzej; Séraphin, Bertrand (7 December 2008). "Endonucleolytic RNA cleavage by a eukaryotic exosome". Nature. 456 (7224): 993–996. Bibcode:2008Natur.456..993L. doi:10.1038/nature07480. PMID 19060886.
  7. ^ Brown, JT; Bai, X; Johnson, AW (March 2000). "The yeast antiviral proteins Ski2p, Ski3p, and Ski8p exist as a complex in vivo". RNA. 6 (3): 449–57. PMC 1369926. PMID 10744028.
  8. ^ Kalisiak, K; Kuliński, TM; Tomecki, R; Cysewski, D; Pietras, Z; Chlebowski, A; Kowalska, K; Dziembowski, A (28 February 2017). "A short splicing isoform of HBS1L links the cytoplasmic exosome and SKI complexes in humans". Nucleic Acids Research. 45 (4): 2068–2080. doi:10.1093/nar/gkw862. PMC 5389692. PMID 28204585.
  9. ^ Saito, S; Hosoda, N; Hoshino, S (14 June 2013). "The Hbs1-Dom34 protein complex functions in non-stop mRNA decay in mammalian cells". The Journal of Biological Chemistry. 288 (24): 17832–43. doi:10.1074/jbc.M112.448977. PMC 3682582. PMID 23667253.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  10. ^ a b c d e Alberts, Bruce (2002). Molecular biology of the cell 4th edition. New York: Garland Science. ISBN 978-0-8153-3218-3.
  11. ^ a b Vasudevan, Shobha; Peltz, Stuart W.; Wilusz, Carol J. (September 2002). "Non-stop decay--a new mRNA surveillance pathway". BioEssays. 24 (9): 785–788. doi:10.1002/bies.10153. ISSN 0265-9247. PMID 12210514.
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