mot-2-Mediated cross talk between nuclear factor-B and p53 is involved in arsenite-induced tumorigenesis of human embryo lung fibroblast cells.
BACKGROUND
Inactivation of p53 is involved in arsenite-induced tumorigenesis; however, the molecular mechanisms remain poorly understood.


OBJECTIVE
We investigated the molecular mechanisms underlying the inactivation of p53 and neoplastic transformation induced by arsenite in human embryo lung fibroblast (HELF) cells.


METHODS
Anchorage-independent growth assays were performed, and tumorigenicity in intact animals was assessed to confirm arsenite-induced neoplastic transformation. We determined the levels and functions of p53, nuclear factor-kappa B (NF-B; a key transcriptional regulator), and mot-2 (a p53 inhibitor) and their relationships in arsenite-induced transformed HELF cells by two-dimensional electrophoresis, reverse-transcriptase polymerase chain reaction, Western blot, immunofluorescence, and co-immunoprecipitation assays.


RESULTS
Exposure of HELF cells to low levels of arsenite increased their proliferation rate and anchorage-independent growth and disrupted normal contact inhibition. When introduced into nude mice, transformed cells were tumorigenic. We used proteomic analysis to identify proteins with altered expression between untreated and arsenite-exposed cells. We found decreased expression of NF-B repressing factor (NKRF; an inhibitor of NF-B-mediated gene transcription), increased expression of mot-2, and increased activation of NF-B. Changes in cells exposed to 1.0 microM arsenite were more marked than changes in cells exposed to 0.5 or 2.0 microM arsenite. Inactivation of NF-B prevented malignant transformation induced by 1.0 microM arsenite. Moreover, we also identified a mechanism whereby NF-B regulated p53. Specifically, activation of NF-B up-regulated mot-2 expression, which prevented nuclear translocation of p53 and switched the binding preference of the p53 and NF-B coactivator CBP [cyclic AMP-responsive element binding protein (CREB) binding protein] from p53 to NF-B.


CONCLUSIONS
mot-2-mediated cross talk between NF-B and p53 appears to be involved in arsenite-induced tumorigenesis of HELF cells.
Li
Yuan
Y
Department of Molecular Cell Biology and Toxicology, Nanjing Medical University, Jiangsu, People's Republic of China.
Xu
Yuan
Y
Ling
Min
M
Yang
Ye
Y
Wang
Shoulin
S
Li
Zhong
Z
Zhou
Jianwei
J
Wang
Xinru
X
Liu
Qizhan
Q
D000818:Animals; D018053:Arsenites / Q000633:toxicity*; D015153:Blotting, Western; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002471:Cell Transformation, Neoplastic / Q000139:chemically induced* / Q000378:metabolism*; D015180:Electrophoresis, Gel, Two-Dimensional; D004622:Embryo, Mammalian / Q000166:cytology; D005347:Fibroblasts; D005455:Fluorescent Antibody Technique; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D047468:Immunoprecipitation; D051379:Mice; D008819:Mice, Nude; D024101:Mitochondrial Proteins; D016328:NF-kappa B / Q000378:metabolism*; D040901:Proteomics; D020239:Receptor Cross-Talk / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
D018053:Arsenites; D018840:HSP70 Heat-Shock Proteins; C492001:HSPA9 protein, human; D024101:Mitochondrial Proteins; D016328:NF-kappa B; D016159:Tumor Suppressor Protein p53; C015001:arsenite