Protein Arginine Methyltransferase 1 (PRMT1)

Protein arginine methylation is catalyzed by arginine methyltransferases. The bulk of methylated arginine residues in eukaryotic cells are found in heterogeneous nuclear ribonucleoproteins (hnRNPs), RNA-binding proteins that play essential roles in the metabolism of nuclear pre-mRNA. Recombinant PRMT1 methylated histones and hnRNPA1 in vitro. The deduced 361-amino acid protein was designated IR1B4 for 'interferon receptor-1-bound protein 4.' Epitope-tagged IR1B4 bound the IFNAR1 intracytoplasmic domain in vitro. Antibodies against IFNAR1 coimmunoprecipitated a methyltransferase activity from human cell extracts. An antisense oligonucleotide strongly reduced methyltransferase activity in human cells, and caused them to become more resistant to growth inhibition by interferon.