Biopolymers in vivo

  • Article
    | Open Access

    Mechanical strength of in situ assembled nuclear lamin filaments arranged in a 3D meshwork is unclear. Here, using mechanical, structural and simulation tools, the authors report the hierarchical organization of the lamin meshwork that imparts strength and toughness to lamin filaments at par with silk and Kevlar®

    • K. Tanuj Sapra
    • , Zhao Qin
    •  & Ohad Medalia
  • Article
    | Open Access

    In vivo experiments and optical tweezers force-spectroscopy measurements assessing the co-translational folding of the G-domain from bacterial elongation factor G reveal a sequential folding pathway initiating from the C-terminus. These results suggest that protein folding and synthesis proceed in opposite directions.

    • Xiuqi Chen
    • , Nandakumar Rajasekaran
    •  & Christian M. Kaiser
  • Article
    | Open Access

    The design principles underlying biomolecular phase separation of membrane-less organelles remain poorly understood. Using model homopolymers, Fisher et al. show that the formation kinetics of coexisting liquid phases can be tuned by exploiting differences between arginine and lysine residues.

    • Rachel S. Fisher
    •  & Shana Elbaum-Garfinkle
  • Article
    | Open Access

    The existence, nature and biological relevance of mechanoradicals in proteins are unknown. Here authors show that mechanical stress on collagen produces radicals and subsequently reactive oxygen species and suggest that collagen I evolved as a radical sponge against mechano-oxidative damage.

    • Christopher Zapp
    • , Agnieszka Obarska-Kosinska
    •  & Frauke Gräter
  • Article
    | Open Access

    The phase separation of two species of associating polymers is suppressed by a magic-number effect for certain combinations of the numbers of binding sites. Here the authors use lattice simulations and analytical calculations to show that this magic-number effect can be greatly enhanced if one component has a rigid shape.

    • Bin Xu
    • , Guanhua He
    •  & Ned S. Wingreen
  • Article
    | Open Access

    The actin homolog MreB directs cell-wall insertion and maintains cell shape in many rod-shaped bacteria. Here, Shi et al. perform molecular dynamics simulations for MreB to extract mechanical parameters for inputs into a coarse-grained biophysical polymer model that predicts MreB filament properties.

    • Handuo Shi
    • , David A. Quint
    •  & Kerwyn Casey Huang
  • Article
    | Open Access

    Fluorogenic RNA aptamers have been used for RNA imaging, but folding and fluorescence stability often limited their use in high resolution applications. Here the authors present an array of stably folding Mango II aptamers for imaging of coding and non-coding RNAs at single-molecule resolution, in both live and fixed cells.

    • Adam D. Cawte
    • , Peter J. Unrau
    •  & David S. Rueda
  • Article
    | Open Access

    The mussel byssus cuticle is a wear-resistant and extensible metalloprotein composite. Here, the authors probed the cuticle nanostructure and composition before, during and after fabrication revealing a crucial role of metal-binding proteins that self-organize via liquid-liquid phase separation.

    • Franziska Jehle
    • , Elena Macías-Sánchez
    •  & Matthew J. Harrington
  • Article
    | Open Access

    Glass transition in soft materials can be affected by the topology of constituent particles, but the detail remains elusive. Here, Smrek et al. show that the interplay between circular topology of ring polymers and their active segments generates a new state of matter, namely active topological glass.

    • Jan Smrek
    • , Iurii Chubak
    •  & Kurt Kremer
  • Article
    | Open Access

    The ability to encapsulate living cells could lead to many applications. Here, the authors present a flexible method to graft DNA polymers onto bacteria, yeast and mammalian cells, polymerize them into DNA cocoons and use these to manipulate and select cells based on the encoded polymer sequences on DNA cocoons.

    • Tao Gao
    • , Tianshu Chen
    •  & Genxi Li
  • Article
    | Open Access

    Antibodies are generated through remote genomic interactions involving immunoglobulin variable (VH), diversity (DH) and joining (JH) gene segments. Here the authors develop a strategy to track VH-DHJH motion in B-lymphocytes and provide evidence that chromosome organisation near the sol-gel phase transition dictates the timing of genomic interactions to orchestrate gene expression and somatic recombination.

    • Nimish Khanna
    • , Yaojun Zhang
    •  & Cornelis Murre
  • Article
    | Open Access

    Bacteria assemble the surface layer (S-layer), a crystalline protein coat surrounding the curved surface, using protein self-assembly. Here authors image native and purified RsaA, the S-layer protein from C. crescentus, and show that protein crystallization alone is sufficient to assemble and maintain the S-layer in vivo.

    • Colin J. Comerci
    • , Jonathan Herrmann
    •  & W. E. Moerner
  • Article
    | Open Access

    During mitosis, tension at the centromere occurs from the spindle but the role of centromere mechanics in controlling metaphase tension is poorly understood. Here, the authors report that mechanical stiffnness of the centromere matures during mitotic progression and is amplified specifically at metaphase.

    • Lauren A. Harasymiw
    • , Damien Tank
    •  & Melissa K. Gardner
  • Article
    | Open Access

    Studying protein kinetics and stability in living organisms is challenging and most studies are performed in cell culture. Here the authors combine meganuclease-mediated transformation and fluorescence-detected temperature-jump microscopy to quantify protein stability in different tissues of living zebrafish.

    • Ruopei Feng
    • , Martin Gruebele
    •  & Caitlin M. Davis
  • Article
    | Open Access

    The promoter variant rs35705950 confers a gain of function to the MUC5B gene and is the dominant risk factor for idiopathic pulmonary fibrosis. Here the authors show that mice overexpressing Muc5b in distal airspaces show impaired mucociliary clearance and increased susceptibility to bleomycin-induced lung fibrosis, and that both characteristics are reduced by treatment with a mucolytic agent.

    • Laura A. Hancock
    • , Corinne E. Hennessy
    •  & David A. Schwartz
  • Article
    | Open Access

    The nucleolus is a membrane-less organelle and both Nucleophosmin (NPM1) and Surfeit locus protein 6 (SURF6) are abundant proteins within the nucleolus. Here the authors employ biophysical methods to study the properties of NPM1-S6N droplets and provide insights into the role of SURF6 in maintaining and modulating the liquid-like structure of the nucleolus.

    • Mylene C. Ferrolino
    • , Diana M. Mitrea
    •  & Richard W. Kriwacki
  • Article
    | Open Access

    Despite their importance in plant development and defence the properties of (1,3)-β-glucan remain largely unknown. Here, the authors find that addition of (1,3)-β-glucans increases the flexibility of cellulose and its resilience to high strain, an effect originating in molecular level interactions.

    • Radwa H. Abou-Saleh
    • , Mercedes C. Hernandez-Gomez
    •  & Yoselin Benitez-Alfonso
  • Article
    | Open Access

    How transcription factors find their targets in vivo is still poorly understood. Here the authors use molecular dynamics simulations to investigate how transcription factors diffuse on chromatin, providing a theoretical framework for understanding the key role of genome conformation in this process.

    • Ruggero Cortini
    •  & Guillaume J. Filion
  • Article
    | Open Access

    Cellular contractility is regulated by the GTPase RhoA, but how local signals are translated to a cell-level response is not known. Here the authors show that targeted RhoA activation results in propagation of force along stress fibres and actin flow, and identify zyxin as a regulator of stress fibre mechanics and homeostasis.

    • Patrick W. Oakes
    • , Elizabeth Wagner
    •  & Margaret L. Gardel
  • Article
    | Open Access

    In vitro models of actin organization show the formation of vortices, asters and stars. Here Fritzsche et al. show that such actin structures form in living cells in a manner dependent on the Arp2/3 complex but not myosin, and such structures influence membrane architecture but not cortex elasticity.

    • M. Fritzsche
    • , D. Li
    •  & C. Eggeling
  • Article
    | Open Access

    The interaction between myosin motors and F-actin is well described, but the impact of actin organization on contractility is not well described. Here the authors use a 2D biomimetic system and computational modelling to show that contractility of isotropic actomyosin is cooperative, and contraction velocity scales with myosin activation area.

    • Ian Linsmeier
    • , Shiladitya Banerjee
    •  & Michael P. Murrell
  • Article |

    The degradation of chitin and cellulose is dependent on the processivity of degrading enzymes. Here, Igarashi et al. use high-speed atomic force microscopy to visualize the movement of two chitinases (ChiA and ChiB) and show them to move in opposite directions, allowing a molecular mechanism to be proposed.

    • Kiyohiko Igarashi
    • , Takayuki Uchihashi
    •  & Masahiro Samejima
  • Article |

    Hagfish slime contains fibres that are produced in gland cells, but how these threads are assembled within the cell is unclear. Here, using electron microscopy and three-dimensional modelling, the authors show that during gland cell maturation the shape of the nucleus changes, permitting the coiling of the threads around it.

    • Timothy Winegard
    • , Julia Herr
    •  & Douglas Fudge
  • Article |

    Encapsulating molecules within supramolecular frameworks for potential biological application is challenging. Bhatiaet al. incorporate a fluorescent polymer within an icosahedral DNA nanocapsule, and show that it can be used to target specific cells in vivoand map pH spatially and temporally.

    • Dhiraj Bhatia
    • , Sunaina Surana
    •  & Yamuna Krishnan