Ionizing radiation and TNF-alpha stimulate gene expression of a Thr/Tyr-protein phosphatase HVH1 and inhibitory factor IkappaB alpha in human squamous carcinoma cells.
Exposure of cells to ionizing radiation (IR) or tumor necrosis factor-alpha (TNF-alpha) results in the stimulation of the DNA binding activities of transcription factors, AP-1 and NF-kappaB. HVH1/CL100, a dual specificity protein phosphatase, may attenuate the AP-1 response by dephosphorylating a key upstream element, mitogen-activated protein kinase (MAPK). The members of IkappaB family of proteins regulate the NF-kappaB response. We examined the effects of IR and TNF-alpha on HVH1 and IkappaB alpha gene expression. Our data demonstrate that IR or TNF-alpha treatment of head and neck squamous carcinoma cells (PCI-04A) increased the steady-state levels of HVH1 and IkappaB alpha mRNAs; however, the induction patterns were different. TNF-alpha treatment led to a relatively prolonged stimulation of HVH1 and IkappaB alpha mRNAs lasting at least 7 h, while IR caused a transient stimulation of these mRNAs and the expression returned to basal levels within 6 h post-IR treatment. Treatment of cells with cycloheximide did not prevent the IR orTNF-alpha-inducible expression of HVH1 and IkappaB alpha genes, indicating that these responses were independent of the new protein synthesis. These data imply that protein phosphatase HVH1 and regulatory factor IkappaB alpha may play important roles in cellular response to IR and TNF-alpha. In addition, the kinetics of responsiveness indicates that the mechanisms of IR and TNF-alpha-induced signalling are distinct.
Kasid
U
U
Department of Radiation Medicine, Lombardi Cancer Center, Georgetown University, Washington, DC 20007, USA.
Wang
F H
FH
Whiteside
T L
TL
D015152:Blotting, Northern; D002294:Carcinoma, Squamous Cell / Q000235:genetics / Q000378:metabolism*; D003513:Cycloheximide / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000187:drug effects* / Q000528:radiation effects*; D015870:Gene Expression / Q000187:drug effects* / Q000235:genetics / Q000528:radiation effects*; D052138:Genes, Neoplasm / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D017027:Protein Tyrosine Phosphatases / Q000096:biosynthesis / Q000187:drug effects* / Q000528:radiation effects*; D012334:RNA, Neoplasm / Q000032:analysis / Q000187:drug effects / Q000528:radiation effects; D011839:Radiation, Ionizing; D013997:Time Factors; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D004268:DNA-Binding Proteins; D012334:RNA, Neoplasm; D014409:Tumor Necrosis Factor-alpha; D003513:Cycloheximide; D017027:Protein Tyrosine Phosphatases