Histone Arginine methyltransferases
Arginine methylation is a function of a class of enzymes called PRMTs (protein arginine methyltransferases). There are 9 types of PRMTs found in humans but only 7 members are reported to methylate histones. They can mediate mono or dimethylation of arginine residues. These enzymes use S-adenosyl-methionine (SAM) as a methyl donor and transfer it to the guanidinium side chain of arginine. Based on the position of methyl group addition, the PRMTs are classified into two types.
Type I PRMTs asymmetrically methylate arginine (N,N-dimethylation). They include CARM1, PRMT1, PRMT2, PRMT3, PRMT6 and PRMT8.
Type II PRMTs symmetrically methylate arginine (N,N'-dimethylation). They include PRMT5 and PRMT7.
We found 7 different arginine methyltransferases present in humans, belonging to the above mentioned classes through literature. PRMTs are generally transcriptional activators but some PRMTs like PRMT6 do catalyse repressive marks. Different PRMTs work in close co-ordination to regulate gene expression. A classic example is the expression of NF-kB target genes that are regulated positively and negatively by CARM1 and PRMT2 respectively. These enzymes respond directly to the nuclear hormone mediated signalling. PRMT5 is strongly implicated in diseases like cancer.
Cytogenetic map of Arginine methyltransferases coding genes| Enzyme (UniprotKB recommended name) | Coding gene/s | Site of histone modification |
|---|---|---|
| Histone-arginine methyltransferase CARM1 | CARM1 | H3R17me1, H3R17me2, H3R2me1, H3R26me1 |
| Protein arginine N-methyltransferase 1 | PRMT1 | H4R3me1, H4R3me2 |
| Protein arginine N-methyltransferase 2 | PRMT2 | |
| Protein arginine N-methyltransferase 5 | PRMT5 | H3R8me2, H4R3me2 |
| Protein arginine N-methyltransferase 6 | PRMT6 | H3R2me2, H4R3me2, H2AR3me2 |
| Protein arginine N-methyltransferase 7 | PRMT7 | |
| Protein arginine N-methyltransferase 8 | PRMT8 |