hGTSE-1 Expression Stimulates Cytoplasmic Localization of p53

J Biol Chem. 2004 Mar 19;279(12):11744-52. doi: 10.1074/jbc.M311123200. Epub 2004 Jan 5.

Abstract

hGTSE-1 (human G(2) and S phase-expressed-1) is a cell cycle-regulated protein mainly localized in the cytoplasm and apparently associated with the microtubules. hGTSE-1 is able to down-regulate levels and activity of the p53 tumor suppressor protein: it binds the C-terminal region of p53 and represses its ability to induce apoptosis after DNA damage. Here we report that, after DNA damage, hGTSE-1 becomes stabilized in a p53-independent way and accumulated in the nucleus. Further characterization of hGTSE-1 localization revealed increased nuclear staining in unstressed cells after treatment with the nuclear export inhibitor leptomycin B, or when a nuclear export signal (NES) located in its C-terminal region was mutated. Finally, we provide evidence that hGTSE-1 ectopic expression, in addition to p53 protein levels down-regulation, is able to enhance cytoplasmic localization of p53. Interestingly, NES-mutated hGTSE-1 accumulates in the nucleus, binds p53 but looses its ability to enhance cytoplasmic redistribution of p53 and to regulate p53 protein levels. Similarly, when wild type hGTSE-1 functions on p53 were analyzed in cells lacking Mdm2, it failed in regulating both p53 localization and protein levels, thus indicating that hGTSE-1 requires an intact NES and functional Mdm2 for the regulation of p53. Our results provide new insights into the mechanism of hGTSE-1 function, whereby its characterized nucleo-cytoplasmic shuttling ability is required to regulate p53.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Blotting, Western
  • Cell Line
  • Cell Nucleus / metabolism
  • Cytoplasm / metabolism*
  • DNA Damage
  • Fluorescent Antibody Technique
  • Humans
  • Microtubule-Associated Proteins / chemistry
  • Microtubule-Associated Proteins / metabolism*
  • Molecular Sequence Data
  • Nuclear Proteins*
  • Precipitin Tests
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-mdm2
  • Sequence Homology, Amino Acid
  • Tumor Suppressor Protein p53 / metabolism*

Substances

  • GTSE1 protein, human
  • Microtubule-Associated Proteins
  • Nuclear Proteins
  • Proto-Oncogene Proteins
  • Tumor Suppressor Protein p53
  • MDM2 protein, human
  • Proto-Oncogene Proteins c-mdm2