Molecular basis for histone N-terminal methylation by NRMT1

Area of Science:

• Biochemistry
• Structural Biology
• Epigenetics

Background:

• NRMT1 (Newt N-terminal methyltransferase 1) is an enzyme involved in protein methylation.
• It targets histone proteins like CENP-A and nonhistone substrates.
• Understanding NRMT1's structure and function is crucial for epigenetics research.

Purpose of the Study:

• To elucidate the crystal structure of human NRMT1 bound to a CENP-A peptide.
• To identify key residues involved in substrate recognition and catalysis.
• To investigate the substrate specificity of NRMT1.

Main Methods:

• X-ray crystallography to determine the structure of NRMT1-CENP-A peptide complex at 1.3 Å resolution.
• Site-directed mutagenesis to identify critical amino acid residues.
• Histone peptide profiling to assess substrate selectivity.
• Co-crystallization of NRMT1 with a fruit fly H2B peptide.

Main Results:

• The crystal structure reveals NRMT1 possesses a methyltransferase fold similar to DOT1L and PRMT, but distinct from SET domain enzymes.
• Mutagenesis studies pinpointed key residues for substrate binding and catalysis.
• NRMT1 exhibits high selectivity for human CENP-A and fruit fly H2B.
• A conserved "Xaa-Pro-Lys/Arg" motif was identified as critical for NRMT1 recognition.

Conclusions:

• The structural and biochemical data provide insights into NRMT1's catalytic mechanism and substrate recognition.
• The identified NRMT1 recognition motif highlights its importance in targeting specific histone substrates.
• This study lays the groundwork for further investigation into NRMT1's role in cellular processes.