We recently identified a novel actin cytoskeleton-associated protein magicin, for merlin and Grb2 interacting cytoskeletal protein. To unravel the cellular functions of magicin, we used a yeast two-hybrid system and identified Fyn tyrosine kinase as a specific binding partner for magicin. Fyn phosphorylates magicin in vitro. In addition to Fyn, Src and Lck also interact with magicin. Upon stimulation with anti-CD3 antibody, magicin is phosphorylated in the T lymphocyte leukemia Jurkat cell line. Magicin phosphorylation is not observed in an Lck-deficient line, J.CaM1.6, indicating that Lck is the major Src family kinase for phosphorylating magicin in Jurkat cells. Employing site-directed mutagenesis along with in vitro kinase assays, we found that Y64 of magicin is phosphorylated by Lck creating a SH2-Grb2 binding motif. Magicin has also been identified as a Mediator subunit (MED28) in the nucleus involved in transcriptional regulation, therefore we propose that magicin may serve as a multi-faceted adaptor/scaffold to relay cellular signaling to the cytoskeleton and from the cytoskeleton to the nucleus.
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MED28 regulates MEK1-dependent cellular migration in human breast cancer cells.
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Department of Nutrition, China Medical University, Taichung, Taiwan, ROC.
MED28, a mammalian Mediator subunit, exhibits several cellular roles, including a merlin, Grb2, and cytoskeleton-associated protein (magicin), a repressor of smooth muscle cell differentiation, and an endothelial-derived gene (EG-1). Overexpression of MED28 may stimulate cell proliferation which presumably results from the transcriptional activation of the Mediator function. Additionally, several tumors, including breast cancer, highly express MED28.
View Article and Find Full Text PDFResveratrol modulates MED28 (Magicin/EG-1) expression and inhibits epidermal growth factor (EGF)-induced migration in MDA-MB-231 human breast cancer cells.
J Agric Food Chem
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Department of Nutrition and Health Sciences, Chang Jung Christian University, Tainan, Taiwan, ROC.
Resveratrol and pterostilbene exhibit diverse biological activities. MED28, a subunit of the mammalian Mediator complex for transcription, was also identified as magicin, an actin cytoskeleton Grb2-associated protein, and as endothelial-derived gene (EG-1). Several tumors exhibit aberrant MED28 expression, whereas the underlying mechanism is unclear.
View Article and Find Full Text PDFElevated MED28 expression predicts poor outcome in women with breast cancer.
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Department of Pathology and Laboratory Medicine, David Geffen School of Medicine at UCLA, Los Angeles, California 90095, USA.
Background: MED28 (also known as EG-1 and magicin) has been implicated in transcriptional control, signal regulation, and cell proliferation. MED28 has also been associated with tumor progression in in vitro and in vivo models. Here we examined the association of MED28 expression with human breast cancer progression.
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The neurofibromatosis 2 (NF2) tumor suppressor protein merlin is commonly mutated in human benign brain tumors. The gene altered in NF2 was located on human chromosome 22q12 in 1993 and the encoded protein named merlin and schwannomin. Merlin has homology to ERM family proteins, ezrin, radixin, and moesin, within the protein 4.
View Article and Find Full Text PDFMediator subunit MED28 (Magicin) is a repressor of smooth muscle cell differentiation.
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Molecular Neurogenetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, Boston 02114, and Department of Cell Biology, Harvard Medical School, Charlestown, Massachusetts 02129, USA.
Magicin, a protein that we isolated earlier as an interactor of the neurofibromatosis 2 protein merlin, was independently identified as MED28, a subunit of the mammalian Mediator complex. Mediator complex is an evolutionarily conserved transcriptional cofactor, which plays an essential role in positive and negative gene regulation. Distinct Mediator subunit composition is thought to contribute to gene regulation specificity based on the interaction of specific subunits with subsets of transcription factors.
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