Study of the G2/M cell cycle checkpoint in irradiated mammary epithelial cells overexpressing Cul-4A gene.
OBJECTIVE
Members of the cullin gene family are known to be involved in cell cycle control. One of the cullin genes, Cul-4A, is amplified and overexpressed in breast cancer cells. This study investigates the effect of Cul-4A overexpression upon G2/M cell cycle checkpoint after DNA damage induced by either ionizing or nonionizing radiation.


METHODS
The normal mammary epithelial cell line MCF10A was stably transfected with full-length Cul-4A cDNA. Independent clones of MCF10A cells that overexpress Cul-4A proteins were selected and treated with either 8 Gy of ionizing radiation or 7 J/M(2) of UV radiation. The profile of cell cycle progression and the accumulation of several cell cycle proteins were analyzed.


RESULTS
We found that overexpression of Cul-4A in MCF10A cells abrogated the G2/M cell cycle checkpoint in response to DNA damage induced by ionizing irradiation, but not to DNA damage induced by nonionizing radiation. Analysis of cell cycle proteins showed that after ionizing irradiation, p53 accumulated in the mock-transfected MCF10A cells, but not in the Cul-4A transfectants.


CONCLUSIONS
Our results suggest a role for Cul-4A in tumorigenesis and/or tumor progression, possibly through disruption of cell cycle control.
Gupta
Anu
A
Geraldine Brush Cancer Research Institute, California Pacific Medical Center, San Francisco, CA 94115, USA.
Yang
Li Xi
LX
Chen
Ling chun
Lc
D001943:Breast Neoplasms / Q000235:genetics / Q000473:pathology / Q000532:radiotherapy*; D018797:Cell Cycle Proteins / Q000378:metabolism; D044842:Cullin Proteins; D004249:DNA Damage; D005260:Female; D005434:Flow Cytometry; D016195:G2 Phase / Q000235:genetics*; D005784:Gene Amplification; D006801:Humans; D008677:Metaphase / Q000235:genetics*; D009363:Neoplasm Proteins / Q000235:genetics* / Q000378:metabolism; D011836:Radiation Tolerance; D014407:Tumor Cells, Cultured / Q000528:radiation effects
C114234:CUL4A protein, human; D018797:Cell Cycle Proteins; D044842:Cullin Proteins; D009363:Neoplasm Proteins