Jianqi Yang, Y. Kawai, R. Hanson
Jul 13, 2001
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Journal
The Journal of Biological Chemistry
Abstract
Sodium butyrate, an erythroid differentiation inducer and a histone deacetylase inhibitor, increases Gαi2 levels in differentiating K562 cells. Here we show that sodium butyrate induces Gαi2 gene transcription via sequences at −50/−36 and −92/−85 in the Gαi2 gene promoter. Both sequences contain core sequence motif for Sp1 binding; electrophoretic mobility shift as well as supershift assays confirmed binding to Sp1. Transcription from the Gαi2 gene promoter was also activated by two other histone deacetylase inhibitors, trichostatin A andHelminthsporium carbonium toxin (HC toxin), which also induce erythroblastic differentiation in K562 cells. However, hydroxyurea, a potent erythroid differentiation inducer in these cells, did not activate transcription from this gene promoter, indicating that promoter activation is inducer-specific. Mutations within the Sp1 sites at −50/−36 and −92/−85 in the Gαi2 gene promoter substantially decreased transcriptional activation by sodium butyrate, trichostatin A, or HC toxin. Transfection with constitutively activated ERKs indicated that this promoter can be activated through the MEK-ERK signal transduction pathway. Inhibition of the MEK-ERK pathway with U0126 or reduction in the expression of endogenous ERK with an antisense oligonucleotide to ERK significantly inhibited sodium butyrate- and HC toxin-induced transcription but had no effect on trichostatin A-induced transcription. Inhibition of the JNK and p38 MAPKs, using selective inhibitors, had no effect on sodium butyrate-induced transcription. In cells in which sodium butyrate induction of promoter activation had been inhibited by various concentrations of U0126, constitutively activated ERK2 reversed this inhibition. These results show that the MEK-ERK signal transduction pathway is important in butyrate signaling, which eventually converges in the cell nucleus.