[Gadd45 mediated G2/M cell cycle arrest induced by BRCA1].
OBJECTIVE
It is considered that tumor suppressor gene BRCA1 is an important factor in the regulation of cell cycle checkpoint, but the molecular mechanism by which BRCA1 regulates cell cycle G(2)/M arrest is less known. The objective of this study was to investigate the effects of Gadd45 on the BRCA1-induced cell growth suppression.


METHODS
BRCA1 induction of Gadd45 protein was analyzed using Western-blot assay following cells transfection with BRCA1 expression vector and cell sorting. Activation of the Gadd45 promoter by BRCA1 was determined by CAT assay. Effect of antisense Gadd45 on the BRCA1-induced cell cycle G(2)-M arrest was examined by flow cytometry analysis. And the effects of antisense Gadd45 on BRCA1-mediated growth suppression in HeLa and HCT116 cell lines was determined by colony formation assay.


RESULTS
Gadd45 protein was highly induced after expression of BRCA1. BRCA1 strongly activated the Gadd45 promoter. Antisense Gadd45 substantially abrogated BRCA1-activated cell cycle G(2)-M arrest and BRCA1-induced cell growth suppression on HeLa and HCT116 cell lines.


CONCLUSIONS
Gadd45 is a BRCA1-regulated downstream gene and mediates the role of BRCA1 in the control of cell cycle G(2)/M arrest and growth suppression.
Song
Yong-Mei
YM
National Key Laboratory of Molecular Oncology, Cancer Institute (Hospital), Chinese Academy of Medical Science, Peking Union Medical College, Beijing, 100021, PR China.
Tong
Tong
T
Fu
Ming
M
Dong
Li-Jia
LJ
Jin
Shun-Qian
SQ
Wu
Min
M
Zhan
Qi-Min
QM
D019313:BRCA1 Protein / Q000378:metabolism / Q000494:pharmacology*; D002455:Cell Division / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D016195:G2 Phase / Q000187:drug effects; D019398:Genes, BRCA1; D045325:HCT116 Cells; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000187:drug effects; D011506:Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D014162:Transfection; D015854:Up-Regulation; D000097642:GADD45 Proteins
D019313:BRCA1 Protein; D047908:Intracellular Signaling Peptides and Proteins; D020319:Oligodeoxyribonucleotides, Antisense; D011506:Proteins; D000097642:GADD45 Proteins