BMK1/ERK5 regulates serum- induced early gene expression through transcription factor MEF2C.
Big MAP kinase 1 (BMK1), also known as ERK5, is a mitogen-activated protein (MAP) kinase member whose biological role is largely undefined. We have shown previously that the activity of BMK1 in rat smooth muscle cells is up-regulated by oxidants. Here, we describe a constitutively active form of the MAP kinase kinase, MEK5(D), which selectively activates BMK1 but not other MAP kinases in vivo. Through utilization of MEK5(D), we have determined that a member of the MEF2 transcription factor family, MEF2C, is a protein substrate of BMK1. BMK1 dramatically enhances the transactivation activity of MEF2C by phosphorylating a serine residue at amino acid position 387 in this transcription factor. Serum is also a potent stimulator of BMK1- induced MEF2C phosphorylation, since a dominant-negative form of BMK1 specifically inhibits serum- induced activation of MEF2C. One consequence of MEF2C activation is increased transcription of the c-jun gene. Taken together, these results strongly suggest that in some cell types the MEK5/BMK1 MAP kinase signaling pathway regulates serum- induced early gene expression through the transcription factor MEF2C.[1]References
- BMK1/ERK5 regulates serum-induced early gene expression through transcription factor MEF2C. Kato, Y., Kravchenko, V.V., Tapping, R.I., Han, J., Ulevitch, R.J., Lee, J.D. EMBO J. (1997) [Pubmed]
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