6r5k

Cryo-EM structure of a poly(A) RNP bound to the Pan2-Pan3 deadenylase

Loading... Status: waiting for Mol* initialization Structural highlights 6r5k is a 7 chain structure with sequence from Baker's yeast. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: MG Gene: PAN2, YGL094C (Baker's yeast), PAB1, YER165W (Baker's yeast), PAN3, ECM35, YKL025C (Baker's yeast) Activity: Poly(A)-specific ribonuclease, with EC number 3.1.13.4 Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function [PAN3_YEAST] Regulatory subunit of the poly(A)-nuclease (PAN) deadenylation complex, one of two cytoplasmic mRNA deadenylases involved in mRNA turnover. PAN specifically shortens poly(A) tails of RNA when the poly(A) stretch is bound by poly(A)-binding protein PAB1, which is followed by rapid degradation of the shortened mRNA tails by the CCR4-NOT complex. Deadenylated mRNAs are then degraded by two alternative mechanisms, namely exosome-mediated 3'-5' exonucleolytic degradation, or deadenlyation-dependent mRNA decaping by DCP1-DCP2 and subsequent 5'-3' exonucleolytic degradation by XRN1. May also be involved in post-transcriptional maturation of mRNA poly(A) tails, trimming the tails from their synthesized length to the slightly shorter, apparently messenger-specific length found on newly exported mRNAs.. PAN3 acts as a positive regulator for PAN activity, recruiting the catalytic subunit PAN2 to mRNA via its interaction with PAB1. PAN cooperates with protein kinase DUN1 in the regulation of RAD5 mRNA levels and cell survival in response to replicational stress. [PAN2_YEAST] Catalytic subunit of the poly(A)-nuclease (PAN) deadenylation complex, one of two cytoplasmic mRNA deadenylases involved in mRNA turnover. PAN specifically shortens poly(A) tails of RNA when the poly(A) stretch is bound by poly(A)-binding protein PAB1, which is followed by rapid degradation of the shortened mRNA tails by the CCR4-NOT complex. Deadenylated mRNAs are then degraded by two alternative mechanisms, namely exosome-mediated 3'-5' exonucleolytic degradation, or deadenlyation-dependent mRNA decaping by DCP1-DCP2 and subsequent 5'-3' exonucleolytic degradation by XRN1. May also be involved in post-transcriptional maturation of mRNA poly(A) tails, trimming the tails from their synthesized length to the slightly shorter, apparently messenger-specific length found on newly exported mRNAs. PAN cooperates with protein kinase DUN1 in the regulation of RAD5 mRNA levels and cell survival in response to replicational stress. [PABP_YEAST] Binds the poly(A) tail of mRNA. Appears to be an important mediator of the multiple roles of the poly(A) tail in mRNA biogenesis, stability and translation. In the nucleus, interacts with the nuclear cleavage factor IA (CFIA), which is required for both mRNA cleavage and polyadenylation. Is also required for efficient mRNA export to the cytoplasm. Acts in concert with a poly(A)-specific nuclease (PAN) to affect poly(A) tail shortening, which may occur concomitantly with either nucleocytoplasmic mRNA transport or translational initiation. Regulates PAN activity via interaction with the stimulator PAN3 or the inhibitor PBP1. In the cytoplasm, affects both translation and mRNA decay. Stimulates translation by interaction with translation initiation factor eIF4G, a subunit of the cap-binding complex eIF4F, bringing the 5'- and 3'-ends of the mRNA in proximity. The formation of this circular mRNP structure appears to be critical for the synergistic effects of the cap and the poly(A) tail in facilitating translation initiation, recycling of ribosomes, and mRNA stability. Also regulates translation termination by recruiting eukaryotic release factor 3 (eRF3). Interaction with eRF3 is also required for regulation of normal mRNA decay through translation termination-coupled poly(A) shortening, probably mediated by PAN. Loss of PAB1 from the mRNP after deadenylation triggers mRNA degradation. Inhibits the major cytoplasmic mRNA deadenylase CCR4-NOT complex. Is also associated peripherally with COPI vesicles through its interaction with ARF1, and this is required for correct localization of the asymmetrically distributed ASH1 mRNA. Publication Abstract from PubMed The stability of eukaryotic mRNAs is dependent on a ribonucleoprotein (RNP) complex of poly(A)-binding proteins (PABPC1/Pab1) organized on the poly(A) tail. This poly(A) RNP not only protects mRNAs from premature degradation but also stimulates the Pan2-Pan3 deadenylase complex to catalyze the first step of poly(A) tail shortening. We reconstituted this process in vitro using recombinant proteins and show that Pan2-Pan3 associates with and degrades poly(A) RNPs containing two or more Pab1 molecules. The cryo-EM structure of Pan2-Pan3 in complex with a poly(A) RNP composed of 90 adenosines and three Pab1 protomers shows how the oligomerization interfaces of Pab1 are recognized by conserved features of the deadenylase and thread the poly(A) RNA substrate into the nuclease active site. The structure reveals the basis for the periodic repeating architecture at the 3' end of cytoplasmic mRNAs. This illustrates mechanistically how RNA-bound Pab1 oligomers act as rulers for poly(A) tail length over the mRNAs' lifetime. Molecular Basis for poly(A) RNP Architecture and Recognition by the Pan2-Pan3 Deadenylase.,Schafer IB, Yamashita M, Schuller JM, Schussler S, Reichelt P, Strauss M, Conti E Cell. 2019 May 14. pii: S0092-8674(19)30399-X. doi: 10.1016/j.cell.2019.04.013. PMID:31104843 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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