Proteomics profiling of arginine methylation defines PRMT5 substrate specificity

Area of Science:

• Biochemistry
• Molecular Biology
• Cancer Research

Background:

• Protein arginine methyltransferases (PRMTs) regulate critical cellular processes.
• PRMT5, a key type II PRMT, is implicated in cell survival, differentiation, and cancer.
• Understanding PRMT5's complex biology and substrate interactions is crucial for cancer therapy.

Purpose of the Study:

• To globally profile arginine methylation changes upon PRMT5 inhibition.
• To identify novel PRMT5 substrates and elucidate its substrate specificity.
• To link PRMT5 functions and inhibition effects to anticancer mechanisms.

Main Methods:

• Utilized a pipeline combining stable isotope labeling with amino acids in cell culture (SILAC) and immunoenriched methyl peptides.
• Employed heavy methyl SILAC for orthogonal validation and reduced false discovery rates.
• Performed in vitro methylation assays to validate PRMT5 targets and enzyme preferences.

Main Results:

• Identified a global profile of arginine monomethylation and symmetric dimethylation after PRMT5 inhibition.
• Discovered previously unknown PRMT5 substrates, expanding knowledge beyond chromatin.
• Provided mechanistic insights into PRMT5's substrate specificity, particularly for Gly-Arg-Gly (GRG) motifs.

Conclusions:

• This study offers comprehensive insights into the global effects of PRMT5 and its inhibition in live cells.
• Refined understanding of PRMT5 substrate specificity, highlighting the GRG motif.
• Provides a foundation for developing targeted cancer therapies by clarifying PRMT5's role.