6trq | pdb_00006trq
S.c. Scavenger Decapping Enzyme DcpS in complex with the capped RNA dinucleotide m7G-GU
Structural highlights
Function[DCPS_YEAST] Decapping scavenger enzyme that catalyzes the cleavage of a residual cap structure following the degradation of mRNAs by the 3'->5' exosome-mediated mRNA decay pathway. Hydrolyzes cap analog structures like 7-methylguanosine nucleoside triphosphate (m7GpppG) and tri-methyl guanosine nucleoside triphosphate (m3(2,2,7)GpppG) with up to 10 nucleotide substrates (small capped oligoribonucleotides) and specifically releases 5'-phosphorylated RNA fragments and 7-methylguanosine monophosphate (m7GMP) or tri-methyl guanosine nucleoside monophosphate (m3(2,2,7)GMP), respectively. Does not hydrolyze unmethylated cap analog (GpppG) and shows no decapping activity on intact m7GpppG-capped mRNA molecules longer than 25 nucleotides. Does not hydrolyze 7-methylguanosine diphosphate (m7GDP) and tri-methylguanosine diphosphate (m3(2,2,7)GDP) to (m(7)GMP) and m3(2,2,7)GMP, respectively (PubMed:22985415). May also play a role in the 5'->3 mRNA decay pathway; m7GDP, the downstream product released by the 5'->3' mRNA mediated decapping activity, may be also converted by DCS1 to m7GMP (PubMed:14523240). Binds to m7GpppG and strongly to m7GDP. May also regulates the 5'->3' exoribonucleolytic mRNA decay pathway in a cap-independent manner. Negatively regulates trehalase activity.[1] [2] [3] [4] [5] [6] [7] Publication Abstract from PubMedThe 5' messenger RNA (mRNA) cap structure enhances translation and protects the transcript against exonucleolytic degradation. During mRNA turnover, this cap is removed from the mRNA. This decapping step is catalyzed by the Scavenger Decapping Enzyme (DcpS), in case the mRNA has been exonucleolyticly shortened from the 3' end by the exosome complex. Here, we show that DcpS only processes mRNA fragments that are shorter than three nucleotides in length. Based on a combination of methyl transverse relaxation optimized (TROSY) NMR spectroscopy and X-ray crystallography, we established that the DcpS substrate length-sensing mechanism is based on steric clashes between the enzyme and the third nucleotide of a capped mRNA. For longer mRNA substrates, these clashes prevent conformational changes in DcpS that are required for the formation of a catalytically competent active site. Point mutations that enlarge the space for the third nucleotide in the mRNA body enhance the activity of DcpS on longer mRNA species. We find that this mechanism to ensure that the enzyme is not active on translating long mRNAs is conserved from yeast to humans. Finally, we show that the products that the exosome releases after 3' to 5' degradation of the mRNA body are indeed short enough to be decapped by DcpS. Our data thus directly confirms the notion that mRNA products of the exosome are direct substrates for DcpS. In summary, we demonstrate a direct relationship between conformational changes and enzyme activity that is exploited to achieve substrate selectivity. Molecular basis of the selective processing of short mRNA substrates by the DcpS mRNA decapping enzyme.,Fuchs AL, Wurm JP, Neu A, Sprangers R Proc Natl Acad Sci U S A. 2020 Jul 28. pii: 2009362117. doi:, 10.1073/pnas.2009362117. PMID:32723815[8] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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