The Methyltransferase WBSCR22/Merm1 Enhances Glucocorticoid Receptor Function and is Regulated in Lung Inflammation and Cancer. [Molecular Bases of Disease]

January 31st, 2014 by Jangani, M., Poolman, T. M., Matthews, L., Yang, N., Farrow, S. N., Berry, A., Hanley, N., Williamson, A. J. K., Whetton, A. D., Donn, R., Ray, D. W.

Glucocorticoids (Gc) regulate cell fate and immune function. We identified the metasasis-promoting methyltransferase, metastasis-related methyltransferase 1 (WBSCR22/Merm1) as a novel glucocorticoid receptor (GR) regulator, relevant to human disease. Merm1 binds the GR co-activator GRIP1, but not GR. Loss of Merm1 impaired both GR transactivation, and transrepression, by reducing GR recruitment to its binding sites. This was accompanied by loss of GR-dependent H3K4Me3 at a well characterised promoter. Inflammation promotes Gc resistance, in part through the actions of TNF α and IFN γ. These cytokines suppressed Merm1 protein expression, by driving ubiquitination of two conserved lysine residues. Restoration of Merm1 expression rescued GR transactivation. Cytokine-suppression of Merm1, and of GR function was also seen in human lung explants. In addition, striking loss of Merm1 protein was observed in both inflammatory and neoplastic human lung pathologies. In conclusion, Merm1 is a novel regulator of chromatin structure affecting GR recruitment and function, contributing to loss of Gc sensitivity in inflammation, with suppressed expression in pulmonary disease.
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