Lysine methylation of progesterone receptor at activation function 1 regulates both ligand independent activity and ligand sensitivity of the receptor [Genomics and Proteomics]

January 10th, 2014 by Chung, H. H., Sze, S. K., Woo, A. R. E., Sun, Y., Sim, K. H., Dong, X. M., Lin, V. C.-L.

Progesterone receptor (PR) exists in two isoforms, PRA and PRB and both contain activation functions AF-1 and AF-2. It is believed that AF-1 is primarily responsible for the ligand-independent activity whereas AF-2 mediates ligand-dependent PR activation. Although more than a dozen of post-translational modifications (PTM) of PR have been reported, no PTM on AF-1 or AF-2 has been reported. Using LC-MS/MS based proteomic analysis, this study revealed AF-1 mono-methylation at K464. Mutational analysis revealed remarkable importance of K464 in regulating PR activity. Single point mutation K464Q or K464A led to ligand-independent PR gel upshift similar to the ligand-induced gel upshift. This upshift was associated with increases in both ligand-dependent and ligand-independent PR phosphorylation and PR activity due to the hyperactivation of AF-1. In contrast, mutation of K464 to the bulkier phenylalanine to mimic the effect of methylation caused drastic decrease in PR activity. Importantly, PR-K464Q also showed heightened ligand sensitivity and this was associated with increases in its functional interaction with transcription co-regulators NCoR1 and SRC-1. These results suggest that mono-methylation of PR at K464 likely plays a repressive role on AF-1 activity and ligand sensitivity.
  • Posted in Journal of Biological Chemistry, Publications
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