c-fos transcriptional activation and repression correlate temporally with the phosphorylation status of TCF.
EGF-induction of human astrocytoma and A431 cells leads to c-fos transcriptional activation and then repression. This could be correlated with changes in the DNA binding characteristics of the c-fos regulatory protein ternary complex factor (TCF) present in nuclear extracts from these cells. Band shifts showed the appearance of induction-related slowly migrating protein-DNA complexes, detected as ternary complexes on the c-fos SRE using a truncated SRF molecule and by direct binding to the Drosophila E74 Ets-protein recognition sequence. By several criteria both types of complexes represented TCF. The appearance of the slow ternary and direct complexes correlated with c-fos transcriptional activation, and their disappearance coincided with the ensuing c-fos shut-off. Blocking c-fos transcriptional repression with the phosphatase inhibitor okadaic acid led to their continued presence. They were sensitive to protein phosphatase 2A but not 1 alpha, and similar slow complexes were formed by partially purified p62TCF phosphorylated by a copurifying kinase activity. Thus the phosphorylation state of TCF correlated strongly with c-fos promoter activity. Since ternary complex formation mediated by full-sized SRF was only slightly affected under comparable conditions, we propose a model for c-fos regulation involving modification of constitutively bound TCF.
Hannover Medical School, Institute for Molecular Biology, Germany.
R
R
Zinck
R A
RA
Hipskind
V
V
Pingoud
A
A
Nordheim
D002455:Cell Division / Q000235:genetics; D004273:DNA, Neoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004988:Ethers, Cyclic / Q000494:pharmacology; D016762:Genes, fos; D006367:HeLa Cells; D006801:Humans; D019319:Okadaic Acid; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D054648:Protein Phosphatase 2; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D004988:Ethers, Cyclic; D014157:Transcription Factors; C072545:p62TCF protein, human; D019319:Okadaic Acid; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2