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Trp-Trp (WW 1 ) domains are compact modules of 38 -40 amino acids long, folded into a three-stranded ␤ sheet, and found in single or tandem repeats in over 25 unrelated cellsignaling proteins (1, 2). Although their binding to prolinebased ligands is now well described (3, 4), little is known about their precise biological function. WW domains form a new family of protein-protein interaction modules targeted to proline residues, analogous to the Src homology (SH) 3 domains (5).Based on their proline-rich sequence binding specificities, WW domains are classified into five distinct groups (6). The N-terminal WW domain of the peptidyl-prolyl isomerase Pin1, an essential regulator at mitotic entry, is grouped among class IV domains, which bind peptides containing a proline residue preceded by a phosphoserine or a phosphothreonine (pSer/ pThr-Pro motif) (7). This latter motif is found in several mitotic Pin1-binding phosphoproteins (8), including the mitotic phosphatase Cdc25 (9, 10) and the microtubule-associated tau () protein (11).Site-directed mutagenesis experiments indicate that Pin1 binds phosphoproteins through its N-terminal WW domain and that the binding site mainly implicates the conserved residues Tyr 18 and Trp 29 (7, 11), which constitute a nearly flat hydrophobic area on the molecular surface of the WW domain. WW domains interacting with the core sequence PPXY, like Yesassociated protein, use the same hydrophobic surface for molecular recognition (3,4,12). However, this hydrophobic binding site alone is not likely to explain the phospho-dependent character of the ligand binding to the Pin1 WW domain.Recently the x-ray crystal structure of the full Pin1 protein bound to a doubly phosphorylated peptide (YpSPTpSPS) from the C-terminal domain (CTD) of RNA polymerase II was reported (13). The protein-peptide interactions are essentially limited to two regions on the WW domain surface. First, a phosphate binding pocket, encompassing the side chains of Ser 11 , Arg 12 , and the backbone amide of Arg 12 , anchors the interacting phosphate moiety via several hydrogen bonds. Second, the aromatic pair Tyr 18 -Trp 29 forms a molecular clamp that constrains the proline at position ϩ1 of the interacting phosphoserine. The peptide ligand binds to the Pin1 WW domain in a N-to C-terminal orientation, in contrast to the C-to N-terminal orientation that is found for two other proline-rich peptides in complex with a group I WW domain (3,14). Other proline recognition domains, such as the SH3 domain of the Caenorhabditis elegans signaling adaptor protein Sem5, can * This project was partly executed in the framework of the Génopole de Lille. The 600-MHz NMR facility used in this study was funded by the European community, the Région Nord-Pas de Calais, CNRS, and the Institut Pasteur de Lille. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 1 The ab...

Section: Discussionmentioning

confidence: 99%

1H NMR Study on the Binding of Pin1 Trp-Trp Domain with Phosphothreonine Peptides

Wintjens

Wieruszeski

Drobecq

et al. 2001

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143

“…The near UV spectrum in particular is a fingerprint of the tertiary structure, and even small structural perturbations can remarkably affect both its intensity and shape. The far-ultraviolet (UV) CD spectrum of both WT and mutant WW are typical of WW domains, having a positive band at 230 nm (44,49). This band is, however, not equally intense in the spectrum of the mutant, suggesting a lower content of secondary structure in the former (Fig.…”

Section: Spr Analysis Suggests a Loss Of Function For The Y65c Mutantmentioning

confidence: 99%

“…This is because the reversible nature of cellular signaling cascades favors weak interactions between the various underlying components (43,44).…”

Section: Binding Profiles Of the Mutated And Wt Ww Domains Onmentioning

confidence: 99%

Y65C Missense Mutation in the WW Domain of the Golabi-Ito-Hall Syndrome Protein PQBP1 Affects Its Binding Activity and Deregulates Pre-mRNA Splicing

Tapia

Nicolaescu

McDonald

et al. 2010

The PQBP1 (polyglutamine tract-binding protein 1) gene encodes a nuclear protein that regulates pre-mRNA splicing and transcription. Mutations in the PQBP1 gene were reported in several X chromosome-linked mental retardation disorders including Golabi-Ito-Hall syndrome. The missense mutation that causes this syndrome is unique among other PQBP1 mutations reported to date because it maps within a functional domain of PQBP1, known as the WW domain. The mutation substitutes tyrosine 65 with cysteine and is located within the conserved core of aromatic amino acids of the domain. We show here that the binding property of the Y65C-mutated WW domain and the full-length mutant protein toward its cognate proline-rich ligands was diminished. Furthermore, in GolabiIto-Hall-derived lymphoblasts we showed that the complex between PQBP1-Y65C and WBP11 (WW domain-binding protein 11) splicing factor was compromised. In these cells a substantial decrease in pre-mRNA splicing efficiency was detected. Our study points to the critical role of the WW domain in the function of the PQBP1 protein and provides an insight into the molecular mechanism that underlies the X chromosome-linked mental retardation entities classified globally as Renpenning syndrome.

“…The structures of the individual FBP21 WW domains are very similar to those of previously solved WW domain structures, and the pairwise r.m.s.d. of the ␤-sheet backbone atoms to the solution structures of WW domains from scPrp40 (7), hsFBP11 (22), mmFBP28 (39) are between 1.0 and 1.6 Å.…”

Section: Ww Domains Mediate the Interaction Of Fbp21 Withmentioning

confidence: 99%

Structure and Function of the Two Tandem WW Domains of the Pre-mRNA Splicing Factor FBP21 (Formin-binding Protein 21)

Huang

Beullens

Zhang

et al. 2009

Human FBP21 (formin-binding protein 21) contains a matrin-type zinc finger and two tandem WW domains. It is a component of the spliceosomes and interacts with several established splicing factors. Here we demonstrate for the first time that FBP21 is an activator of pre-mRNA splicing in vivo and that its splicing activation function and interaction with the splicing factor SIPP1 (splicing factor that interacts with PQBP1 and PP1) are both mediated by the two tandem WW domains of group III. We determined the solution structure of the tandem WW domains of FBP21 and found that the WW domains recognize peptide ligands containing either group II (PPLP) or group III (PPR) motifs. The binding interfaces involve both the XP and XP2 grooves of the two WW domains. Significantly, the tandem WW domains of FBP21 are connected by a highly flexible region, enabling their simultaneous interaction with two proline-rich motifs of SIPP1. The strong interaction between SIPP1 and FBP21 can be explained by the conjugation of two low affinity interactions with the tandem WW domains. Our study provides a structural basis for understanding the molecular mechanism underlying the functional implication of FBP21 and the biological specificity of tandem WW domains.Gene expression in eukaryotic cells involves several steps, including transcription, mRNA processing, and export. Pre-mRNA splicing takes place in the spliceosome, a highly dynamic ribonucleoprotein particle that consists of five small nuclear RNAs and at least 150 proteins. Small nuclear ribonucleoproteins (snRNPs) 3 and numerous protein factors are essential for the formation of the active spliceosome (1, 2). In budding yeast, the splicing factor Prp40 participates in crossintron bridging by interacting with the branch point-binding protein (BBP) and the U5 snRNP component Prp8. Prp40 contacts the 5Ј splice site and interacts with BBP, bringing the 5Ј splice site and the branch point in spatial proximity. These interactions are believed to be conserved in mammals (3-5). FBP21 (formin-binding protein 21), the mammalian Prp40-like protein, colocalizes with splicing factors in nuclear storage sites for pre-mRNA splicing factors. In addition, FBP21 is a component of the mammalian spliceosomal A/B complex and is associated with U2 snRNPs (6). FBP21 interacts directly with the splicing factors U1 snRNP protein U1C, the core snRNP proteins SmB and SmBЈ, and the branch point-binding protein SF1/mBBP, suggesting that it may also play a role in crossintron bridging of U1 and U2 snRNPs in the spliceosomes. FBP21 contains a matrin-type zinc finger and two group III WW domains ( Fig. 1) that are structurally related to those of the established splicing factors U1C and Prp40, respectively (6, 7). The binding of FBP21 to splicing factors is mediated by its tandem WW domains, which represent interaction modules for proline-rich ligands (4, 8, 9). Although the above data strongly suggest that FBP21 has a role in pre-mRNA splicing, there are no in vivo data to support this contention. The splicing...