Detection of cyclin b1 expression in g(1)-phase cancer cell lines and cancer tissues by postsorting Western blot analysis.
Protein complex of cyclin B1 and cyclin-dependent protein kinase 1 induces phosphorylation of key substrates that mediate cell cycle transition during the G(2)-M phase. It is believed that cyclin B1 accumulates in the S phase of the cell cycle and reaches the maximal level at mitosis but is absent in G(1)-phase cells. In the present study, we demonstrated that cyclin B1 was expressed in the arrested G(1)-phase MOLT-4 lymphocyte leukemia cells and in G(1) phase T-7 transitional tumor cells, as determined by flow cytometry. In addition, we showed that cyclin B1 was detected in the G(1) phase in breast cancer cells from patient tissues and in lymphocytes from patients with leukemia. These findings were confirmed for the first time by postsorting Western blot analysis and by confocal microscopy. Furthermore, by using postsorting Western blotting, we found that cyclin B1 was expressed in different time-window sections of the G(1) phase under different conditions. For the asynchronously growing T-7 cells, cyclin B1 was detected in early G(1) phase, whereas in MOLT-4 cells arrested in G(1)-S phase, cyclin B1 was mainly detected in late G(1) phase. We propose that the cyclin B1 expressed in the G(1) phase may differ from that expressed in the G(2)-M phase, and that this unscheduled type of cyclin B1 may play an important role in tumorigenesis and apoptosis.
Tongji Cancer Institute and Center for Molecular Medicine, Department of Surgery, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei Province, People's Republic of China.
Manli
M
Shen
Yongdong
Y
Feng
Chun
C
Gao
Deding
D
Tao
Junbo
J
Hu
Eddie
E
Reed
Qingdi Q
QQ
Li
Jianping
J
Gong
D015153:Blotting, Western; D045744:Cell Line, Tumor; D019926:Cyclin B / Q000032:analysis* / Q000502:physiology; D056744:Cyclin B1; D005260:Female; D016193:G1 Phase; D006801:Humans; D018613:Microscopy, Confocal; D009369:Neoplasms / Q000737:chemistry* / Q000473:pathology
C534699:CCNB1 protein, human; D019926:Cyclin B; D056744:Cyclin B1