Self assembly of NuMA: multiarm oligomers as structural units of a nuclear lattice

EMBO J. 1999 Mar 15;18(6):1689-700. doi: 10.1093/emboj/18.6.1689.

Abstract

NuMA is a nuclear matrix protein in interphase and relocates to the spindle poles in mitotis. Different NuMA constructs, in which either N- or C-terminal domains were deleted, and the full-length construct were expressed in Escherichia coli, and the NuMA polypeptides were purified to homogeneity and allowed to assemble in vitro. Electron microscopy showed that NuMA can build multiarm oligomers by interaction of the C-terminal globular domains. Each arm of the oligomer corresponds to a NuMA dimer. Oligomers with up to 10 or 12 arms have been observed for both full-length NuMA and for constructs that still contain the proximal part of the C-terminal tail domain. Other results from this laboratory have shown that transient overexpression of NuMA in HeLa cells induces a nuclear scaffold with a quasi-hexagonal organization that can fill the nuclei. Here we show that computer modelling of the three-dimensional packing of NuMA into such scaffolds can explain the different spacing of the hexagons seen when constructs with different coiled-coil lengths are used. Thus, the 12 arm oligomer, for which we have in vitro evidence, may be the structural unit from which the nuclear scaffold in transfected cells is built.

MeSH terms

  • Antigens, Nuclear
  • Cell Cycle Proteins
  • Cell Nucleus / metabolism
  • Cell Nucleus / ultrastructure
  • Cloning, Molecular
  • Computer Simulation
  • Escherichia coli
  • HeLa Cells
  • Humans
  • Macromolecular Substances
  • Microscopy, Electron
  • Models, Molecular
  • Nuclear Matrix-Associated Proteins
  • Nuclear Proteins / chemistry*
  • Nuclear Proteins / genetics
  • Nuclear Proteins / ultrastructure*
  • Protein Structure, Secondary
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / ultrastructure
  • Sequence Deletion
  • Spindle Apparatus / metabolism
  • Spindle Apparatus / ultrastructure

Substances

  • Antigens, Nuclear
  • Cell Cycle Proteins
  • Macromolecular Substances
  • NUMA1 protein, human
  • Nuclear Matrix-Associated Proteins
  • Nuclear Proteins
  • Recombinant Fusion Proteins