A coupled fluorescent assay for histone methyltransferases.

Area of Science:

• Biochemistry
• Molecular Biology
• Epigenetics

Background:

• Histone methyltransferases (HMTs) regulate gene transcription via methylation of histones.
• Quantitative assays for HMTs are crucial for understanding their roles but remain challenging.
• HMTs catalyze S-adenosylmethionine (AdoMet)-dependent methylation of histone residues.

Purpose of the Study:

• To develop a robust, coupled-fluorescence-based assay for quantifying AdoMet-dependent methyltransferase activity.
• To characterize the substrate specificity and kinetics of HMTs, specifically Schizosaccharomyces pombe CLR4.
• To provide a facile method for assessing the enzymatic activity of various methyltransferases.

Main Methods:

• Development of a coupled-fluorescence assay utilizing S-adenosylhomocysteine hydrolase (SAHH).
• SAHH hydrolyzes S-adenosylhomocysteine (AdoHcy) to homocysteine (Hcy) and adenosine (Ado).
• Homocysteine concentration is determined using a thiol-sensitive fluorophore.

Main Results:

• The assay successfully determined kinetic parameters for the methylation of a histone H3 peptide by CLR4.
• Demonstrated the utility of the assay for HMTs, including the H3 Lys-9-specific methyltransferase CLR4.
• The assay provides rapid and facile determination of HMT kinetics.

Conclusions:

• The developed fluorescent SAHH-coupled assay is effective for quantitative analysis of HMT activity.
• This assay can be adapted to study a broad range of AdoMet-dependent methyltransferases.
• Facilitates research into the epigenetic roles of histone methylation and HMT enzymes.