A protein kinase (q.v.) that functions in cellular signal transduction (q.v.). Janus kinases phosphorlyate specific tyrosine residues in substrate proteins. The gene (JAK 2) which encodes the enzyme is located at 9p24. One function of the JAK 2 protein is to control the responses of erythroblasts to erythropoietin (q.v.). Base substitutions at certain positions in the JAK 2 gene cause polycythemia vera (q.v.).
Subjects: Genetics and Genomics.