Phosphorylation-mediated inactivation of coactivator-associated arginine methyltransferase 1

Area of Science:

• Molecular Biology
• Epigenetics
• Gene Regulation

Background:

• Protein arginine methyltransferases, including CARM1, are crucial for activating nuclear receptor-dependent transcription.
• CARM1-mediated histone methylation is a known transcriptional activator.
• The precise regulation of CARM1 enzymatic activity remains largely uncharacterized.

Purpose of the Study:

• To investigate the regulatory mechanisms governing the enzymatic activity of CARM1.
• To elucidate the role of post-translational modifications, specifically phosphorylation, in CARM1 function.
• To understand how CARM1 regulation impacts estrogen receptor-mediated transcription.

Main Methods:

• Site-directed mutagenesis was employed to mimic phosphorylation at a conserved serine residue in CARM1.
• Assays were conducted to assess the methyl donor (S-adenosylmethionine) binding affinity of wild-type and mutant CARM1.
• Histone methylation activity and CARM1-mediated transactivation of estrogen receptor were evaluated.

Main Results:

• Phosphorylation at a conserved serine residue negatively regulates CARM1 methyltransferase activity.
• A serine-to-glutamic acid mutation, mimicking phosphorylation, reduced CARM1's ability to bind S-adenosylmethionine and methylate histones.
• This mutation also inhibited CARM1's coactivation of estrogen receptor-dependent transcription.

Conclusions:

• CARM1 enzymatic activity is subject to negative regulation by phosphorylation.
• Phosphorylation of CARM1 provides a novel mechanism for the inactivation of CARM1 and subsequent downregulation of estrogen-dependent gene expression.
• This study offers a key insight into the post-translational control of protein arginine methyltransferases.