The Arginine/Lysine-Rich Element within the DNA-Binding Domain Is Essential for Nuclear Localization and Function of the Intracellular Pathogen Resistance 1

PLoS One. 2016 Sep 13;11(9):e0162832. doi: 10.1371/journal.pone.0162832. eCollection 2016.

Abstract

The mouse intracellular pathogen resistance 1 (Ipr1) gene plays important roles in mediating host immunity and previous work showed that it enhances macrophage apoptosis upon mycobacterium infection. However, to date, little is known about the regulation pattern of Ipr1 action. Recent studies have investigated the protein-coding genes and microRNAs regulated by Ipr1 in mouse macrophages, but the structure and the functional motif of the Ipr1 protein have yet to be explored. In this study, we analyzed the domains and functional motif of the Ipr1 protein. The resulting data reveal that Ipr1 protein forms a homodimer and that the Sp100-like domain mediates the targeting of Ipr1 protein to nuclear dots (NDs). Moreover, we found that an Ipr1 mutant lacking the classic nuclear localization signal (cNLS) also translocated into the nuclei, suggesting that the cNLS is not the only factor that directs Ipr1 nuclear localization. Additionally, mechanistic studies revealed that an arginine/lysine-rich element within the DNA-binding domain (SAND domain) is critical for Ipr1 binding to the importin protein receptor NPI-1, demonstrating that this element plays an essential role in mediating the nuclear localization of Ipr1 protein. Furthermore, our results show that this arginine/lysine-rich element contributes to the transcriptional regulation and apoptotic activity of Ipr1. These findings highlight the structural foundations of Ipr1 action and provide new insights into the mechanism of Ipr1-mediated resistance to mycobacterium.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Arginine / chemistry
  • Cell Nucleus / metabolism
  • DNA / metabolism
  • HEK293 Cells
  • Humans
  • Lysine / chemistry
  • Macrophages / metabolism
  • Macrophages / microbiology
  • Mice
  • Models, Molecular
  • Mutant Proteins / chemistry
  • Mutant Proteins / genetics
  • Mutant Proteins / metabolism
  • Mycobacterium tuberculosis / pathogenicity
  • NIH 3T3 Cells
  • Nuclear Localization Signals / chemistry
  • Nuclear Localization Signals / genetics
  • Nuclear Localization Signals / metabolism
  • Protein Domains
  • Protein Multimerization
  • RAW 264.7 Cells
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Sequence Homology, Amino Acid
  • Trans-Activators / chemistry*
  • Trans-Activators / genetics
  • Trans-Activators / metabolism*
  • alpha Karyopherins / metabolism

Substances

  • Ifi75 protein, mouse
  • KPNA1 protein, mouse
  • Mutant Proteins
  • Nuclear Localization Signals
  • Recombinant Fusion Proteins
  • Trans-Activators
  • alpha Karyopherins
  • DNA
  • Arginine
  • Lysine

Grant support

This work was supported by National Natural Science Foundation of China (Grant No. 31530075).