Research Highlight Janus Kinase 2: An Epigenetic ‘Writer ’ that Activates Leukemogenic Genes

Activation of Janus kinase 2 (JAK2) plays a critical role in normal hematopoiesis and leukemogenesis. Dawson et al. (2009; JAK2 phosphorylates histone H3Y41 and excludes HP1alpha from chromatin. Nature 461, 819–822) report that JAK2 performs this function by displacing the heterochromatin protein HP1a from chromatin through phosphorylation of histone H3. Activation of the Janus kinase 2 (JAK2) pathway plays an important role in both normal hematopoiesis and hematological malignancies (Neubauer et al., 1998; Tefferi et al., 2005). Past studies have demonstrated that the function of JAK2 in hematopoiesis and leukemogenesis is mediated through cytoplasmic phos-phorylation of the various signal transdu-cer and activator of transcription (STATs), which are subsequently translocated into the nucleus to activate STAT target gene