AMPK-beta1 subunit is a p53-independent stress responsive protein that inhibits tumor cell growth upon forced expression.
In an effort to search for genes responsible for cell growth arrest and/or apoptosis associated with p53 signaling pathways, we profiled a human lung carcinoma line H1299, expressing a temperature-sensitive p53 (V138) against Affymetric human U95Av2 GeneChip A, consisting of 12 000 genes. 133 genes were identified that were either induced or repressed in response to p53-dependent cell growth arrest and apoptotic conditions. Among them, the beta1 subunit, but not other subunits of the AMP-activated protein kinase (AMPK) was strongly induced. The p53 consensus binding site search in the AMPK-beta1 promoter and the first intron identified four such putative sites. However, p53 failed to bind to any of these sites as assayed by in vitro gel retardation and in vivo chromatin immunoprecipitation. Furthermore, northern analysis showed that induction of this gene is independent of p53, as increased expression of the gene was observed in p53 null H1299/Neo control cells when the temperature was shifted to 32 degrees C. Moreover, a DNA damaging agent, etoposide, also induced beta1 subunit expression in multiple human tumor cells, regardless of p53 status. Thus, the beta1 subunit of AMPK is not a p53 downstream target gene, but can be induced by cold shock or the chemotherapeutic drug, etoposide in a p53-independent manner. To determine the biological significance of AMPK-beta1 induction, we over-expressed the gene in two tumor cell lines, H1299 and U2-OS. In both lines, forced AMPK-beta1 expression inhibits tumor cell growth, suggesting that AMPK-beta1 induction may facilitate stress-induced growth inhibition and cell killing.
Li
Jun
J
Cancer Molecular Sciences, Pfizer Global Research and Development, Ann Arbor Laboratories, 2800 Plymouth Road, MI 48105, USA.
Jiang
Ping
P
Robinson
Megan
M
Lawrence
Theodore S
TS
Sun
Yi
Y
D055372:AMP-Activated Protein Kinases; D017209:Apoptosis; D001483:Base Sequence; D015153:Blotting, Western; D003080:Cold Temperature; D024202:Electrophoretic Mobility Shift Assay; D005047:Etoposide / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008175:Lung Neoplasms / Q000378:metabolism / Q000473:pathology*; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes; D020411:Oligonucleotide Array Sequence Analysis; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics*; D011494:Protein Kinases / Q000096:biosynthesis* / Q000235:genetics; D017346:Protein Serine-Threonine Kinases; D021122:Protein Subunits; D015533:Transcriptional Activation; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000187:drug effects; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D015854:Up-Regulation
D009097:Multienzyme Complexes; D021122:Protein Subunits; D016159:Tumor Suppressor Protein p53; D005047:Etoposide; D011494:Protein Kinases; C526182:PRKAB1 protein, human; D017346:Protein Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases