2a1r
From Proteopedia
Crystal structure of PARN nuclease domain
Structural highlights
FunctionPARN_HUMAN 3'-exoribonuclease that has a preference for poly(A) tails of mRNAs, thereby efficiently degrading poly(A) tails. Exonucleolytic degradation of the poly(A) tail is often the first step in the decay of eukaryotic mRNAs and is also used to silence certain maternal mRNAs translationally during oocyte maturation and early embryonic development. Interacts with both the 3'-end poly(A) tail and the 5'-end cap structure during degradation, the interaction with the cap structure being required for an efficient degradation of poly(A) tails. Involved in nonsense-mediated mRNA decay, a critical process of selective degradation of mRNAs that contain premature stop codons. Also involved in degradation of inherently unstable mRNAs that contain AU-rich elements (AREs) in their 3'-UTR, possibly via its interaction with KHSRP. Probably mediates the removal of poly(A) tails of AREs mRNAs, which constitutes the first step of destabilization.[1] [2] [3] [4] [5] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedPoly(A)-specific ribonuclease (PARN) is a processive, poly(A)-specific 3' exoribonuclease. The crystal structure of C-terminal truncated human PARN determined in two states (free and RNA-bound forms) reveals that PARNn is folded into two domains, an R3H domain and a nuclease domain similar to those of Pop2p and epsilon186. The high similarity of the active site structures of PARNn and epsilon186 suggests that they may have a similar catalytic mechanism. PARNn forms a tight homodimer, with the R3H domain of one subunit partially enclosing the active site of the other subunit and poly(A) bound in a deep cavity of its nuclease domain in a sequence-nonspecific manner. The R3H domain and, possibly, the cap-binding domain are involved in poly(A) binding but these domains alone do not appear to contribute to poly(A) specificity. Mutations disrupting dimerization abolish both the enzymatic and RNA-binding activities, suggesting that the PARN dimer is a structural and functional unit. The cap-binding domain may act in concert with the R3H domain to amplify the processivity of PARN. Structural insight into poly(A) binding and catalytic mechanism of human PARN.,Wu M, Reuter M, Lilie H, Liu Y, Wahle E, Song H EMBO J. 2005 Dec 7;24(23):4082-93. Epub 2005 Nov 10. PMID:16281054[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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