The nuclear dot protein sp100, characterization of domains necessary for dimerization, subcellular localization, and modification by small ubiquitin-like modifiers

J Biol Chem. 1999 Apr 30;274(18):12555-66. doi: 10.1074/jbc.274.18.12555.

Abstract

The Sp100 and promyelocytic leukemia proteins (PML) are constituents of nuclear domains, known as nuclear dots (NDs) or PML bodies, and are both covalently modified by the small ubiquitin-related protein SUMO-1. NDs play a role in autoimmunity, virus infections, and in the etiology of acute promyelocytic leukemia. To date, little is known about the function of the Sp100 protein. Here we analyzed Sp100 domains that determine its subcellular localization, dimerization, and SUMOylation. A functional nuclear localization signal and an ND-targeting region that coincides with an Sp100 homodimerization domain were mapped. Sequences similar to the Sp100 homodimerization/ND-targeting region occur in several other proteins and constitute a novel protein motif, termed HSR domain. The lysine residue of the Sp100 protein, to which SUMO-1 is covalently linked, was mapped within and may therefore modulate the previously described HP1 protein-binding site. A consensus sequence for SUMOylation of proteins in general is suggested. SUMOylation strictly depended on a functional nuclear localization signal but was not necessary for nuclear import or ND targeting. A three-dimensional structure of Sp100, which supports the mapping data and provides additional information on Sp100 structure/function relationships, was generated by computer modeling. Taken together, our studies indicate the existence of well defined Sp100 domains with functions in ND targeting, nuclear import, nuclear SUMOylation, and protein-protein interaction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Antigens, Nuclear*
  • Autoantigens / chemistry
  • Autoantigens / genetics
  • Autoantigens / metabolism*
  • Base Sequence
  • DNA Primers
  • Dimerization
  • Models, Molecular
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Nuclear Proteins / chemistry
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Peptide Fragments / chemistry
  • Peptide Fragments / metabolism
  • Sequence Homology, Amino Acid
  • Subcellular Fractions / metabolism*
  • Ubiquitins / chemistry*

Substances

  • Antigens, Nuclear
  • Autoantigens
  • DNA Primers
  • Nuclear Proteins
  • Peptide Fragments
  • Ubiquitins
  • SP100 protein, human