Cell-cycle-dependent three-dimensional redistribution of nuclear proteins, P 120, pKi-67, and SC 35 splicing factor, in the presence of the topoisomerase I inhibitor camptothecin.
Topoisomerase I (Topo I) is mostly known for its role in DNA relaxation, which is required for duplication and transcription. Topo I acts as a protein kinase mainly directed to the mRNA splicing factor SC35. Camptothecin is one of the specific Topo I inhibitors and is effective on the two functions of the enzyme. In this study we demonstrated that treatment of KB cells with camptothecin for only 30 min induced the 3D reorganization and redistribution of three proteins involved in the nucleus machinery, P 120, pKi-67, and SC 35, and this occurred in a cell cycle-dependent manner. Our data were obtained from confocal microscopic studies after immunolabeling, 3D reconstruction, and measurement of the nuclear components volumes. In the presence of camptothecin, P 120, which occupied the nucleolar volume, lost its reticulation and pKi-67 was redistributed within the nucleoplasm and even into the cytoplasm. Finally, for SC 35 the fusion of its dots into bigger volumes was observed specifically during the G1 phase. Variations of volumes were also observed for the nucleolus and for the nucleus. These results pointed out that, depending on the cell cycle phase, Topo I functions were selective toward the three different proteins.
Elias
Emmanuel
E
Unité Médian, UMR CNRS 6142, UFR Pharmacie, IFR 53, 1 rue du Maréchal Juin, F 51096 Reims cedex, France.
Lalun
Nathalie
N
Lorenzato
Marianne
M
Blache
Laurent
L
Chelidze
Pavel
P
O'Donohue
Marie-Françoise
MF
Ploton
Dominique
D
Bobichon
Hélène
H
D002166:Camptothecin / Q000494:pharmacology*; D002451:Cell Compartmentation / Q000187:drug effects* / Q000502:physiology; D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D003593:Cytoplasm / Q000187:drug effects / Q000201:enzymology; D004264:DNA Topoisomerases, Type I / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D016193:G1 Phase / Q000187:drug effects / Q000235:genetics; D006801:Humans; D019394:Ki-67 Antigen / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D012261:Ribonucleoproteins; D000068103:Serine-Arginine Splicing Factors; D059004:Topoisomerase I Inhibitors; D020729:p120 GTPase Activating Protein / Q000235:genetics / Q000378:metabolism
D016895:Culture Media, Serum-Free; D004791:Enzyme Inhibitors; D019394:Ki-67 Antigen; D009687:Nuclear Proteins; D012261:Ribonucleoproteins; D059004:Topoisomerase I Inhibitors; D020729:p120 GTPase Activating Protein; C073288:SRSF2 protein, human; D000068103:Serine-Arginine Splicing Factors; D004264:DNA Topoisomerases, Type I; D002166:Camptothecin