title: Lipopolysaccharide-induced methylation of HuR, an mRNA-stabilizing protein, by CARM1. Coactivator-associated arginine methyltransferase.
abstract: The RNA-binding protein HuR stabilizes labile mRNAs carrying AU-rich instability elements. This mRNA stabilization can be induced by hypoxia, lipopolysaccharide, and UV light. The mechanism by which these stimuli activate HuR is unclear and might be related to post-translational modification of this protein. Here we show that HuR can be methylated on arginine. However, HuR is not a substrate for PRMT1, the most prominent protein-arginine methyltransferase in mammalian cells, which methylates a number of heterogeneous nuclear ribonucleoproteins. Instead, HuR is specifically methylated by coactivator-associated arginine methyltransferase 1 (CARM1), a protein-arginine methyltransferase previously shown to serve as a transcriptional coactivator. By analyzing methylation of specific HuR arginine-to-lysine mutants and by sequencing radioactively methylated HuR peptides, Arg(217) was identified as the major HuR methylation site. Arg(217) is located in the hinge region between the second and third of the three HuR RNA recognition motif domains. Antibodies against a methylated HuR peptide were used to demonstrate in vivo methylation of HuR. HuR methylation increased in cells that overexpressed CARM1. Importantly, lipopolysaccharide stimulation of macrophages, which leads to HuR-mediated stabilization of tumor necrosis factor alpha mRNA in these cells, caused increased methylation of endogenous HuR. Thus, CARM1, which plays a role in transcriptional activation through histone H3 methylation, may also play a role in post-transcriptional gene regulation by methylating HuR.
authors.affiliation: Department of Pathology, University of Southern California, Keck School of Medicine, Los Angeles, California 90089-9176, USA.
authors.forename: Hongwei
authors.initials: H
authors.lastname: Li
authors.forename: Sungmin
authors.initials: S
authors.lastname: Park
authors.forename: Britta
authors.initials: B
authors.lastname: Kilburn
authors.forename: Mary Anne
authors.initials: MA
authors.lastname: Jelinek
authors.forename: Agnes
authors.initials: A
authors.lastname: Henschen-Edman
authors.forename: Dana W
authors.initials: DW
authors.lastname: Aswad
authors.forename: Michael R
authors.initials: MR
authors.lastname: Stallcup
authors.forename: Ite A
authors.initials: IA
authors.lastname: Laird-Offringa
mesh_terms: D000818:Animals; D000954:Antigens, Surface; D001120:Arginine / Q000378:metabolism; D002460:Cell Line; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; D005786:Gene Expression Regulation; D006801:Humans; D008070:Lipopolysaccharides / Q000378:metabolism* / Q000494:pharmacology; D008264:Macrophages / Q000166:cytology / Q000187:drug effects; D008745:Methylation; D011485:Protein Binding; D011484:Protein-Arginine N-Methyltransferases / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000954:Antigens, Surface; D051959:ELAV Proteins; D000067780:ELAV-Like Protein 1; C098770:ELAVL1 protein, human; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; D001120:Arginine; D011484:Protein-Arginine N-Methyltransferases; C119966:coactivator-associated arginine methyltransferase 1