6wre | pdb_00006wre
Crystal structure of mouse DXO in complex with 5'-OH RNA substrate mimic and calcium ion
Structural highlights
FunctionDXO_MOUSE Ribonuclease that specifically degrades pre-mRNAs with a defective 5' end cap and is part of a pre-mRNA capping quality control. Has decapping, pyrophosphohydrolase and 5'-3' exonuclease activities. Has decapping activity toward incomplete 5' end cap mRNAs such as unmethylated 5' end-capped RNA to release GpppN and 5' end monophosphate RNA. The 5' end monophosphate RNA is then degraded by the 5'-3' exoribonuclease activity, enabling this enzyme to decap and degrade incompletely capped mRNAs. Also possesses RNA 5'-pyrophosphohydrolase activity by hydrolyzing the 5' end triphosphate to release pyrophosphates.[1] Publication Abstract from PubMedModifications at the 5'-end of RNAs play a pivotal role in determining their fate. In eukaryotes, the DXO/Rai1 family of enzymes removes numerous 5'-end RNA modifications, thereby regulating RNA turnover. Mouse DXO catalyzes the elimination of incomplete 5'-end caps (including pyrophosphate) and the non-canonical NAD+ cap on mRNAs, and possesses distributive 5'-3' exoribonuclease activity toward 5'-monophosphate (5'-PO4) RNA. Here, we demonstrate that DXO also catalyzes the hydrolysis of RNAs bearing a 5'-hydroxyl group (5'-OH RNA). The crystal structure of DXO in complex with a 5'-OH RNA substrate mimic at 2.0 A resolution provides elegant insight into the molecular mechanism of this activity. More importantly, the structure predicts that DXO first removes a dinucleotide from 5'-OH RNA. Our nuclease assays confirm this prediction and demonstrate that this 5'-hydroxyl dinucleotide hydrolase (HDH) activity for DXO is higher than the subsequent 5'-3' exoribonuclease activity for selected substrates. Fission yeast Rai1 also has HDH activity although it does not have 5'-3' exonuclease activity, and the Rat1-Rai1 complex can completely degrade 5'-OH RNA. An Arabidopsis DXO1 variant is active toward 5'-OH RNA but prefers 5'-PO4 RNA. Collectively, these studies demonstrate the diverse activities of DXO/Rai1 and expands the collection of RNA substrates that can undergo 5'-3' mediated decay. A novel 5'-hydroxyl dinucleotide hydrolase activity for the DXO/Rai1 family of enzymes.,Doamekpor SK, Gozdek A, Kwasnik A, Kufel J, Tong L Nucleic Acids Res. 2020 Jan 10;48(1):349-358. doi: 10.1093/nar/gkz1107. PMID:31777937[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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