Site specificity of histone H4 methylation by wheat germ protein-arginine N-methyltransferase

Genome-wide localization of histone 4 arginine 3 methylation in a differentiation primed myeloid leukemia cell line

Methylation of arginine residues in proteins is involved in modulation of various protein-protein interactions. At the chromatin level H4R3 methylation provides a signal integration step during myeloid differentiation. In order to globally characterize the role of arginine methylation in signal integration and developmental processes we decided to map genomic loci marked by protein arginine methyl transferase 1 (PRMT1) via histone H4 arginine 3 methylation. For this, we used the myeloid leukemia cell line, HL60, which is known to differentiate along the monocyte/macrophage or granulocyte lineage. We used chromatin immunoprecipitation with an antibody specific for the H4 arginine 3 methyl epitope followed by cloning to isolate genomic loci marked by this modification. After sequencing and in silico analysis we found that all of the genomic hits identified were intronic or within 5 kb of 5' ends of specific genes. The locations identified were enriched in conserved transcription factor binding sites of POU2F1, MEF-2 and FOXL1 factors. A significant number of the genes in the proximity of the identified genomic loci are involved in signaling pathways and developmental processes including immune response of myeloid cells.

Protein interfaces in signaling regulated by arginine methylation

Posttranslational modifications are well-known effectors of signal transduction. Arginine methylation is a covalent modification that results in the addition of methyl groups to the nitrogen atoms of the arginine side chains. A probable role of arginine methylation in signal transduction is emerging with the identification of new arginine-methylated proteins. However, the functional consequences of arginine methylation and its mode of regulation remain unknown. The identification of the protein arginine methyltransferase family and the development of methylarginine-specific antibodies have raised renewed interest in this modification during the last decade. Arginine methylation was mainly observed on abundant proteins such as RNA-binding proteins and histones, but recent advances have revealed a plethora of arginine-methylated proteins implicated in a variety of cellular processes, including signaling by interferon and cytokines, and in T cell signaling. We discuss these recent advances and the role of arginine methylation in signal transduction.

RNA and protein interactions modulated by protein arginine methylation

This review summarizes the current status of protein arginine N-methylation reactions. These covalent modifications of proteins are now recognized in a number of eukaryotic proteins and their functional significance is beginning to be understood. Genes that encode those methyltransferases specific for catalyzing the formation of asymmetric dimethylarginine have been identified. The enzyme modifies a number of generally nuclear or nucleolar proteins that interact with nucleic acids, particularly RNA. Postulated roles for these reactions include signal transduction, nuclear transport, or a direct modulation of nucleic acid interactions. A second methyltransferase activity that symmetrically dimethylates an arginine residue in myelin basic protein, a major component of the axon sheath, has also been characterized. However, a gene encoding this activity has not been identified to date and the cellular function for this methylation reaction has not been clearly established. From the analysis of the sequences surrounding known arginine methylation sites, we have determined consensus methyl-accepting sequences that may be useful in identifying novel substrates for these enzymes and may shed further light on their physiological role.