Chfr interacts and colocalizes with TCTP to the mitotic spindle.
Chfr is a checkpoint protein that plays an important function in cell cycle progression and tumor suppression, although its exact role and regulation are unclear. Previous studies have utilized overexpression of Chfr to determine the signaling pathway of this protein in vivo. In this study, we demonstrate, by using three different antibodies against Chfr, that the endogenous and highly overexpressed ectopic Chfr protein is localized and regulated differently in cells. Endogenous and lowly expressed ectopic Chfr are cytoplasmic and localize to the spindle during mitosis. Higher expression of ectopic Chfr correlates with a shift in the localization of this protein to the nucleus/PML bodies, and with a block of cell proliferation. In addition, endogenous and lowly expressed ectopic Chfr is stable throughout the cell cycle, whereas when highly expressed, ectopic Chfr is actively degraded during S-G2/M phases in an autoubiquitination and proteasome-dependent manner. A two-hybrid screen identified TCTP as a possible Chfr-interacting partner. Biochemical analysis with the endogenous proteins confirmed this interaction and identified beta-tubulin as an additional partner for Chfr, supporting the mitotic spindle localization of Chfr. The Chfr-TCTP interaction was stable throughout the cell cycle, but it could be diminished by the complete depolymerization of the microtubules, providing a possible mechanism where Chfr could be the sensor that detects microtubule disruption and then activates the prophase checkpoint.
Burgess
A
A
Universités Montpellier 2 et 1, Centre de Recherche de Biochimie Macromoléculaire, CNRS UMR 5237, IFR 122, Labellisée Ligue Nationale Contre le Cancer, Montpellier Cedex, France.
Labbé
J-C
JC
Vigneron
S
S
Bonneaud
N
N
Strub
J M
JM
Van Dorsselaer
A
A
Lorca
T
T
Castro
A
A
D000818:Animals; D014408:Biomarkers, Tumor / Q000032:analysis / Q000502:physiology*; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000032:analysis / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D008870:Microtubules / Q000502:physiology; D009363:Neoplasm Proteins / Q000032:analysis / Q000502:physiology*; D010766:Phosphorylation; D000075223:Poly-ADP-Ribose Binding Proteins; D008941:Spindle Apparatus / Q000737:chemistry*; D014404:Tubulin / Q000378:metabolism; D000090324:Tumor Protein, Translationally-Controlled 1; D044767:Ubiquitin-Protein Ligases; D054875:Ubiquitination; D014981:Xenopus
D014408:Biomarkers, Tumor; D018797:Cell Cycle Proteins; D009363:Neoplasm Proteins; D000075223:Poly-ADP-Ribose Binding Proteins; C000715647:TPT1 protein, human; D014404:Tubulin; D000090324:Tumor Protein, Translationally-Controlled 1; C412002:CHFR protein, human; D044767:Ubiquitin-Protein Ligases