HiJAKing the Methylosome in Myeloproliferative Disorders

JAK2 gain-of-function mutations have been shown to cause myeloproliferative neoplasms. In this issue of Cancer Cell, Liu et al. (2011) demonstrate that these JAK2 mutants, but not wild-type JAK2, directly phosphorylate PRMT5 and inhibit its arginine methyltransferase activity, establishing a link between mutant JAK2 and histone arginine methylation.