As JAK1 and JAK2 modulate epigenetic regulation of gene transcription through tyrosine phosphorylation of the histone protein H3 in leukemic- and B cell lymphoma- cell lines [30,31], we performed in vitro kinase assays to address whether JAK3 was also able to phosphorylate Histone H3. The gene discussed is JAK2; the disease is B-cell non-Hodgkin lymphoma.