Mammalian Protein Arginine Methyltransferase 7 (PRMT7) Specifically Targets RXR Sites in Lysine- and Arginine-rich Regions

You Feng; Ranjan Maity; Julian P. Whitelegge; Andrea Hadjikyriacou; Ziwei Li; Cecilia Zurita-Lopez; Qais Al-Hadid; Amander T. Clark; Mark T. Bedford; Jean-Yves Masson; Steven G. Clarke

doi:10.1074/jbc.M113.525345

Mammalian Protein Arginine Methyltransferase 7 (PRMT7) Specifically Targets RXR Sites in Lysine- and Arginine-rich Regions*

From the Departments of ^‡Chemistry and Biochemistry and
^‖Molecular, Cellular, and Developmental Biology, Molecular Biology Institute, UCLA, Los Angeles, California 90095,
the ^§Genome Stability Laboratory, Laval University Cancer Research Center, Hôtel-Dieu de Québec Research Center, Québec G1R 2J6, Canada,
the ^¶Pasarow Mass Spectrometry Laboratory, NPI-Semel Institute for Neuroscience and Human Behavior UCLA, Los Angeles, California 90095, and
the ^**Department of Molecular Carcinogenesis, University of Texas MD Anderson Cancer Center, Smithville, Texas 78957

↵1 To whom correspondence should be addressed: Dept. of Chemistry and Biochemistry and the Molecular Biology Institute, UCLA, 607 Charles E. Young Dr. East, Los Angeles, CA. Tel.: 310-825-8754; Fax: 310-825-1968; E-mail: clarke{at}chem.ucla.edu.

Background: Protein arginine methyltransferase 7 (PRMT7) is associated with various functions and diseases, but its substrate specificity is poorly defined.

Results: Insect cell-expressed PRMT7 forms ω-monomethylarginine residues at basic RXR sequences in peptides and histone H2B.

Conclusion: PRMT7 is a type III PRMT with a unique substrate specificity.

Significance: Novel post-translational modification sites generated by PRMT7 may regulate biological function.

Abstract

The mammalian protein arginine methyltransferase 7 (PRMT7) has been implicated in roles of transcriptional regulation, DNA damage repair, RNA splicing, cell differentiation, and metastasis. However, the type of reaction that it catalyzes and its substrate specificity remain controversial. In this study, we purified a recombinant mouse PRMT7 expressed in insect cells that demonstrates a robust methyltransferase activity. Using a variety of substrates, we demonstrate that the enzyme only catalyzes the formation of ω-monomethylarginine residues, and we confirm its activity as the prototype type III protein arginine methyltransferase. This enzyme is active on all recombinant human core histones, but histone H2B is a highly preferred substrate. Analysis of the specific methylation sites within intact histone H2B and within H2B and H4 peptides revealed novel post-translational modification sites and a unique specificity of PRMT7 for methylating arginine residues in lysine- and arginine-rich regions. We demonstrate that a prominent substrate recognition motif consists of a pair of arginine residues separated by one residue (RXR motif). These findings will significantly accelerate substrate profile analysis, biological function study, and inhibitor discovery for PRMT7.

Footnotes

↵* This work was supported, in whole or in part, by National Institutes of Health Grants GM026020 (to S. G. C.), S10 RR023045 (to J. P. W.), and DK62248 (to M. T. B.). This work was also supported by the Canadian Institute of Health Research (to J. Y. M.).