Growth retardation, polyploidy, and multinucleation induced by Clast3, a novel cell cycle-regulated protein.
We have identified a novel gene, Clast3, by subtraction of cDNAs derived from activated and naive B lymphocytes. Clast3 expression is elevated in cycling cells and down-regulated in cells undergoing growth arrest, indicating that its expression is controlled in a cell cycle-dependent manner. The deduced amino acid sequence of Clast3 cDNA exhibits no significant homology to the known proteins in mammalian and other species. Immunofluorescence staining revealed that Clast3 localizes into discrete nuclear foci. Forced expression of Clast3 results in growth retardation, polyploidy, and generation of multinucleated cells. Treatment of Clast3 transfectants with nocodazole, a spindle-damaging agent, greatly enhances the incidence of the multinucleated cells, suggesting that Clast3 overexpression impairs the same checkpoint activated by nocodazole. Down-regulation of Clast3 expression by antisense oligonucleotides results in a decrease of cells at G(2)-M phase and a concomitant increase of apoptotic cells. These findings indicate that Clast3 is a novel cell cycle-regulated protein and that its constitutive overexpression induces polyploidy and multinucleation by interfering with the mitotic spindle checkpoint.
Bahar
Rumana
R
Division of Pathology, Chiba Cancer Center Research Institute, Chiba 260-8717, Japan.
O-Wang
Jiyang
J
Kawamura
Kiyoko
K
Seimiya
Mika
M
Wang
Yanqing
Y
Hatano
Masahiko
M
Okada
Seiji
S
Tokuhisa
Takeshi
T
Watanabe
Takeshi
T
Tagawa
Masatoshi
M
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology; D001483:Base Sequence; D015152:Blotting, Northern; D015153:Blotting, Western; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism / Q000502:physiology*; D002455:Cell Division; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D018076:DNA, Complementary / Q000378:metabolism; D015536:Down-Regulation; D016195:G2 Phase; D051379:Mice; D008810:Mice, Inbred C57BL; D008938:Mitosis; D008969:Molecular Sequence Data; D015739:Nocodazole / Q000494:pharmacology; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D011003:Ploidies; D011485:Protein Binding; D013154:Spleen / Q000166:cytology; D013997:Time Factors; D014162:Transfection; D014407:Tumor Cells, Cultured
D018797:Cell Cycle Proteins; C469365:Clast3 protein, mouse; D018076:DNA, Complementary; D016376:Oligonucleotides, Antisense; D015739:Nocodazole