hGTSE-1 expression stimulates cytoplasmic localization of p53.
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.
Monte
Martin
M
Laboratorio Nazionale del Consorzio Interuniversitario per le Biotecnologie LNCIB, Area Science Park, Padriciano 99, 34012 Trieste, Italy.
Benetti
Roberta
R
Collavin
Licio
L
Marchionni
Luigi
L
Del Sal
Giannino
G
Schneider
Claudio
C
D000595:Amino Acid Sequence; D015153:Blotting, Western; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism*; D004249:DNA Damage; D005455:Fluorescent Antibody Technique; D006801:Humans; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D011233:Precipitin Tests; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2; D017386:Sequence Homology, Amino Acid; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
C115080:GTSE1 protein, human; D008869:Microtubule-Associated Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2