In this study, we show that the ETS transcription factor ER81 directly binds to and activates the promoter of the matrix metalloproteinase gene, MMP-1. Further, the oncoprotein HER2/Neu synergizes with ER81 to stimulate MMP-1 transcription. The activation of ER81 by HER2/Neu is mediated by MAP kinases, which phosphorylate ER81 in its N-terminal activation domain. Four respective phosphorylation sites have been identified. Blocking phosphorylation at these sites decreases ER81 transcriptional activity, which can be further diminished by abolishment of phosphorylation at two non-MAP kinase sites. Altogether, our results reveal mechanisms of how phosphorylation of ER81 regulates the expression of target genes such as MMP-1, which may be important for many physiological processes from embryogenesis to adulthood as well as for tumor metastasis.
Bibliographical noteFunding Information:
We thank Dr J Travis, Dr Y Yarden and Dr J Cooper for generously providing the pGL2-MMP-1 reporter plasmid, the pLSV-HER2/Neu-V664E expression plasmid and the MKK7a expression plasmid, respectively. We further extend our thanks to Dr P Roche for providing the breast tumor samples and to K Rossow for providing the ER81 recombinant protein. DG Bosc is a research fellow of the National Cancer Institute of Canada supported with funds provided by the Terry Fox Run. This work was supported by the Mayo Foundation, the Mayo Clinic Cancer Center, a grant from the National Cancer Institute (CA85257), and a scholarship (to R Janknecht) from the Sidney Kimmel Foundation for Cancer Research.
- Gene transcription
- MAP kinase
- Matrix metalloproteinase-1
- Protein phosphorylation