Repression of NF-kappaB impairs HeLa cell proliferation by functional interference with cell cycle checkpoint regulators.
NF-kappaB is an inducible transcription factor, which is regulated by interaction with inhibitory IkappaB proteins. Previous studies linked the activity of NF-kappaB to the proliferative state of the cell. Here we have analysed the function of NF-kappaB in the cell cycle. Inhibition of NF-kappaB in HeLa cells by stable overexpression of a transdominant negative IkappaB-alpha protein reduced cell growth. A kinetic analysis of the cell cycle revealed a retarded G1/S transition. The IkappaB-alpha overexpressing cell clones showed a decreased percentage of cells in the S phase and an impaired incorporation of bromodeoxyuridine (BrdU). The amounts of cyclins A, B1, D1, D3, and E were unchanged, but the G1-specific proteins cyclin D2 and cdk2 were strongly elevated in the IkappaB-alpha overexpressing cell clones. These cell clones also displayed an increase in cyclin D1-dependent kinase activity, pointing to a cell cycle arrest at the late G1 phase. IkappaB-alpha overexpression crosstalked to cell cycle checkpoints via a reduction of transcription factor p53 and elevation of p21WAF. Surprisingly, the IkappaB-alpha overexpressing cells showed an enrichment of c-Myc in the nucleoli, although the total amount of c-Myc protein was unchanged. These experiments identify an important contribution of the NF-kappaB/IkappaB system for the growth of HeLa cells.
Kaltschmidt
B
B
Molecular Neurobiology Laboratory, Institute of Anatomy, Albert-Ludwigs-University, Freiburg, Germany.
Kaltschmidt
C
C
Hehner
S P
SP
Dröge
W
W
Schmitz
M L
ML
D002453:Cell Cycle; D002455:Cell Division; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D016193:G1 Phase; D015870:Gene Expression; D006367:HeLa Cells; D006801:Humans; D020672:I-kappa B Proteins; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors*; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism*; D016196:S Phase; D015398:Signal Transduction; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D016328:NF-kappa B; C000606204:NFKBIA protein, human; D016271:Proto-Oncogene Proteins c-myc; D016159:Tumor Suppressor Protein p53; D000072000:NF-KappaB Inhibitor alpha