Biology subjects

Debler, E. W.

Publications and source records attributed to Debler, E. W..

4 recordsLinked to original sources

bioRxiv2022

Structure of the pre-mRNA leakage 39-kDa proteinreveals a single domain of integrated zf-C3HC and Rsm1 modules

In Saccharomyces cerevisiae, the pre-mRNA leakage 39-kDa protein (ScPml39) was reported to retain unspliced pre-mRNA prior to export through nuclear pore complexes (NPCs). Pml39 homologs outside the Saccharomycetaceae family are currently unknown, and mechanistic insight into Pml39 function is lacking. Here we determined the crystal structure of ScPml39 at 2.5 [A] resolution to facilitate the discovery of orthologs beyond Saccharomycetaceae, e.g. in Schizosaccharomyces pombe or human. The crystal structure revealed integrated zf-C3HC and Rsm1 modules, which are tightly associated through a hydrophobic interface to form a single domain. Both zf-C3HC and Rsm1 modules belong to the Zn-containing BIR (Baculovirus IAP repeat)-like super family, with key residues of the canonical BIR domain being conserved. Features unique to the Pml39 modules refer to the spacing between the Zn-coordinating residues, giving rise to a substantially tilted helix aC in the zf-C3HC and Rsm1 modules, and an extra helix AB in the Rsm1 module. Conservation of key residues responsible for its distinct features identifies S. pombe Rsm1 and Homo sapiens NIPA/ZC3HC1 as structural orthologs of ScPml39. Based on the recent functional characterization of NIPA/ZC3HC1 as a scaffold protein that stabilizes the nuclear basket of the NPC, our data suggest an analogous function of ScPml39 in S. cerevisiae.

biochemistry↗

bioRxiv2021

Coil-to-Helix Transition at the Nup358-BicD2 Interface for Dynein Recruitment and Activation

Nup358, a nuclear pore protein, facilitates a nuclear positioning pathway that is essential for many biological processes, including neuromuscular and brain development. Nup358 binds and activates the auto-inhibited dynein adaptor Bicaudal D2 (BicD2), which in turn recruits and activates the dynein machinery to position the nucleus. However, the molecular details of the Nup358/BicD2 interaction remain poorly understood. Here, we show that a minimal Nup358 domain activates dynein/dynactin/BicD2 for processive motility on microtubules. Using nuclear magnetic resonance (NMR) titration and chemical exchange saturation transfer (CEST), a Nup358 helix encompassing residues 2162-2184 was identified, which transitioned from random coil to an -helix upon BicD2-binding and formed the core of the Nup358-BicD2 interface. Mutations in this region of Nup358 decreased the Nup358/BicD2 interaction, resulting in decreased dynein recruitment and impaired motility. BicD2 thus recognizes the cargo adaptor Nup358 though a "cargo recognition -helix", a structural feature that may stabilize BicD2 in its activated state and promote processive dynein motility.

biophysics↗

bioRxiv2019

Structural Basis of Protein Arginine Methyltransferase Activation by a Catalytically Dead Homolog (Prozyme)

Prozymes are pseudoenzymes that stimulate the function of weakly active enzymes through complex formation. The major Trypanosoma brucei protein arginine methyltransferase, TbPRMT1 enzyme (ENZ), requires TbPRMT1 prozyme (PRO) to form an active heterotetrameric complex. Here we present the x-ray crystal structure of the ENZ-{Delta}52PRO tetrameric complex with the cofactor product S-adenosyl-L-homocysteine (AdoHcy) at 2.4 [A] resolution. The individual ENZ and PRO units adopt the highly-conserved PRMT domain architecture and form an antiparallel heterodimer that corresponds to the canonical homodimer observed in all previously reported PRMTs. In turn, two such heterodimers assemble into a tetramer both in the crystal and in solution with twofold rotational symmetry. ENZ is unstable in absence of PRO and incapable of forming a homodimer due to a steric clash of a non-conserved tyrosine within the dimerization arm, rationalizing why PRO is required to complement ENZ to form a PRMT dimer that is necessary, but not sufficient for PRMT activity. The PRO structure deviates from other, active PRTMs in that it lacks the conserved {eta}2 310-helix within the Rossmann fold, abolishing co-factor binding. In addition to its chaperone function for ENZ, PRO substantially contributes to substrate binding. Heterotetramerization is required for catalysis, since heterodimeric ENZ-PRO mutants lack binding affinity and methyltransferase activity towards the substrate protein TbRGG1. Together, we provide a structural basis for PRMT1 ENZ activation by PRO heterotetramer formation, which is conserved across all kinetoplastids, and describe a chaperone function of the PRMT1 prozyme, which represents a novel mode of PRMT regulation.\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=109 SRC=\"FIGDIR/small/776112v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (56K):\norg.highwire.dtl.DTLVardef@3d970dorg.highwire.dtl.DTLVardef@187f03forg.highwire.dtl.DTLVardef@1adee39org.highwire.dtl.DTLVardef@1f30f34_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG HighlightsO_LIThe crystal structure of Trypanosoma brucei protein arginine methyltransferase 1 (PRMT1) is reported\nC_LIO_LITwo enzyme-prozyme heterodimers form a stable heterotetramer essential for catalysis\nC_LIO_LIThe catalytically dead prozyme lacks elements essential for AdoMet binding\nC_LIO_LIThe enzyme alone is unstable and cannot form a canonical dimer due to steric clashes\nC_LIO_LIT. brucei PRMT1 prozyme adopts a chaperone function conserved across kinetoplastids\nC_LI

biochemistry↗

bioRxiv2019

Role of coiled-coil registry shifts in activation of human Bicaudal D2 for dynein recruitment upon cargo-binding

Dynein adaptors such as Bicaudal D2 (BicD2) recognize cargo for dynein-dependent transport. BicD2-dependent transport pathways are important for brain and muscle development. Cargo-bound adaptors are required to activate dynein for processive transport, but the mechanism of action is elusive. Here, we report the structure of the cargo-binding domain of human BicD2 that forms a dimeric coiled-coil with homotypic registry, in which both helices are aligned. To investigate if BicD2 can switch to an asymmetric registry, where a portion of one helix is vertically shifted, we performed molecular dynamics simulations. Both registry types are stabilized by distinct conformations of F743. For the F743I variant, which increases dynein recruitment in the Drosophila homolog, and for the human R747C variant, which causes spinal muscular atrophy, spontaneous coiled-coil registry shifts are observed, which may cause the BicD2-hyperactivation phenotype and disease. We propose that a registry shift upon cargo-binding activates auto-inhibited BicD2 for dynein recruitment.\n\nHighlightsO_LIStable, bona fide BicD2 coiled-coils with distinct registries can be formed.\nC_LIO_LIWe provide evidence that a human disease mutation causes a coiled-coil registry shift.\nC_LIO_LIA coiled-coil registry shift could relieve BicD2-autoinhibition upon cargo-binding.\nC_LIO_LIThe ability to undergo registry shifts may be an inherent property of coiled-coils.\nC_LI\n\nIn BriefOur results support that stable coiled-coils of BicD2 with distinct registries can be formed, and suggest a molecular mechanism for such registry switches. We provide evidence that disease-causing mutations in coiled-coils may alter the equilibrium between registry-shifted conformers, which we propose as a general mechanism of pathogenesis for coiled-coils.\n\nGraphical Abstract O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

biophysics↗