Biology:RNase R
RNase R, or Ribonuclease R, is a 3'-->5' exoribonuclease, which belongs to the RNase II superfamily, a group of enzymes that hydrolyze RNA in the 3' - 5' direction. RNase R has been shown to be involved in selective mRNA degradation, particularly of non stop mRNAs in bacteria.[1][2] RNase R has homologues in many other organisms. When a part of another larger protein has a domain that is very similar to RNase R, this is called an RNase R domain.
Role in trans-translation and ribosomal quality control
RNase R ensures translation accuracy, correct rRNA maturation and elimination of abnormal rRNAs, and is employed by the trans-translation system to break down damaged mRNAs.[3]
In Escherichia coli, RNase R is a 92 kD protein, with the characteristic capacity to degrade structured RNA substrates without displaying sequence specificity. Therefore, RNase R acts over a range of substrates, such as, ribosomal, transfer, messenger and small non-coding RNAs. RNase R is associated with ribonucleoprotein complex that contains tmRNA and SmpB, and is involved in the development of tmRNA under cold-shock.[3]
RNase R is also associated with ribosomes and participates in rRNA, or ribosomal RNA, quality control processes. RNase R has an in vitro affinity for rRNA. In several rRNA quality control pathways, RNase R behaves as a mainfactor by enhancing the removal of faulty rRNA molecules. This protein is also critical for handling rRNA precursors and for observing the ribosome integrity.[3]
RNA digestion
RNase R has two cold shock domains, an RNase catalytic domain, an S1 domain and a basic domain.[4]
Overabundance of RNase R in a cell are harmful since RNase R is more active and more effective in breaking down RNAs than the other bacterial exoribonucleases, such as RNase II.[5] Besides the substrate RNAs that construct double-stranded RNA with 3' overhangs shorter than seven nucleotides, RNase R can degrade all linear RNAs.[6] For the methodical digestion of eukaryotic linear RNAs, RNase R is a good 3' to 5' exoribonuclease but there are infrequent cases of RNase R resistance. Since mRNAs are not chemically protected at their 3' ends, unlike the protection provided at their 5' ends by the cap structure, RNase R successfully degrades linear mRNAs from their unprotected 3' ends.[4]
References
- ↑ "An important role for RNase R in mRNA decay". Molecular Cell 17 (2): 313–8. January 2005. doi:10.1016/j.molcel.2004.11.048. PMID 15664199.
- ↑ "Non-stop mRNA decay: a special attribute of trans-translation mediated ribosome rescue". Frontiers in Microbiology 5: 93. 2014. doi:10.3389/fmicb.2014.00093. PMID 24653719.
- ↑ 3.0 3.1 3.2 "The role of RNase R in trans-translation and ribosomal quality control". Biochimie 114: 113–8. July 2015. doi:10.1016/j.biochi.2014.12.012. PMID 25542646.
- ↑ 4.0 4.1 "A view of pre-mRNA splicing from RNase R resistant RNAs". International Journal of Molecular Sciences 15 (6): 9331–42. May 2014. doi:10.3390/ijms15069331. PMID 24865493.
- ↑ "Purification and characterization of the Escherichia coli exoribonuclease RNase R. Comparison with RNase II". The Journal of Biological Chemistry 277 (24): 21624–9. June 2002. doi:10.1074/jbc.M202942200. PMID 11948193.
- ↑ "Substrate recognition and catalysis by the exoribonuclease RNase R". The Journal of Biological Chemistry 281 (40): 29769–75. October 2006. doi:10.1074/jbc.M606744200. PMID 16893880.
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