title: Structural basis for polyadenosine-RNA binding by Nab2 Zn fingers and its function in mRNA nuclear export.
abstract: Polyadenylation regulation and efficient nuclear export of mature mRNPs both require the polyadenosine-RNA-binding protein, Nab2, which contains seven CCCH Zn fingers. We describe here the solution structure of fingers 5-7, which are necessary and sufficient for high-affinity polyadenosine-RNA binding, and identify key residues involved. These Zn fingers form a single structural unit. Structural coherence is lost in the RNA-binding compromised Nab2-C437S mutant, which also suppresses the rat8-2 allele of RNA helicase Dbp5. Structure-guided Nab2 variants indicate that dbp5(rat8-2) suppression is more closely linked to hyperadenylation and suppression of mutant alleles of the nuclear RNA export adaptor, Yra1, than to affinity for polyadenosine-RNA. These results indicate that, in addition to modulating polyA tail length, Nab2 has an unanticipated function associated with generating export-competent mRNPs, and that changes within fingers 5-7 lead to suboptimal assembly of mRNP export complexes that are more easily disassembled by Dbp5 upon reaching the cytoplasm.
authors.affiliation: Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 0QH, UK.
authors.forename: Christoph
authors.initials: C
authors.lastname: Brockmann
authors.forename: Sharon
authors.initials: S
authors.lastname: Soucek
authors.forename: Sonja I
authors.initials: SI
authors.lastname: Kuhlmann
authors.forename: Katherine
authors.initials: K
authors.lastname: Mills-Lujan
authors.forename: Seth M
authors.initials: SM
authors.lastname: Kelly
authors.forename: Ji-Chun
authors.initials: JC
authors.lastname: Yang
authors.forename: Nahid
authors.initials: N
authors.lastname: Iglesias
authors.forename: Francoise
authors.initials: F
authors.lastname: Stutz
authors.forename: Anita H
authors.initials: AH
authors.lastname: Corbett
authors.forename: David
authors.initials: D
authors.lastname: Neuhaus
authors.forename: Murray
authors.initials: M
authors.lastname: Stewart
mesh_terms: D021581:Active Transport, Cell Nucleus; D000241:Adenosine / Q000737:chemistry*; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D017124:Conserved Sequence; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D019906:Nuclear Magnetic Resonance, Biomolecular; D029543:Nucleocytoplasmic Transport Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011108:Polymers / Q000737:chemistry*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D034443:RNA Transport; D012333:RNA, Messenger / Q000737:chemistry*; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D013499:Surface Properties; D013816:Thermodynamics; D016335:Zinc Fingers
chemical_list: C080773:NAB2 protein, S cerevisiae; D029543:Nucleocytoplasmic Transport Proteins; D011108:Polymers; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; C069424:polyadenosine; D000241:Adenosine