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Janus Kinase 2 is a non-receptor janus kinase, a protein which is part of the tyrosine kinases. These group of kinases are the primary intracellular mediators of cytokine signaling and are involved in the control of cellular growth. As a non-receptor kinase, Jak 2 has a cytoplasmic enzyme which catalyzes the transfer of a phosphate group through phosphorylation to the tyrosine residue in the protein.  Such an enzyme plays a crucial role in regulating various cellular functions by switching on or off additional enzymes within the cell. <ref> Hanks, SK., Quinn, AM., Hunter, T. (1988). The protein kinase family: conserved features and deduced phylogeny of the catalytic domains. Science 241 (4861): 42–52. doi:10.1126/science.3291115. PMID 3291115. </ref> Such phosphorylation is a reversible process, and used in many different pathways as a method to control cellular activity. However kinases like Jak2, have enzymes which add phosphate groups to hydroxyl side chains as can be seen in the diagram. <ref> Hudel, H. “Center for Biomembrane Systems at UC Irvine” http://bass.bio.uci.edu </ref> [[Image:Phosphorylation.png]]

Jak2 was given its name "Janus" after the two-faced Roman God "Janus" who was known as the custodian of the universe and the God of new beginnings. <ref> Kirwan, J. (02, 2011 03). Janus incarnate. Retrieved from http://rense.com/general92/janus.htm http://rense.com/general92/janus.htm </ref> The abbreviation 'Jak' is commonly referred to as 'just another kinase' as, when it was first discovered, the kinase's role was not yet fully understood. <ref> Weinberg, I. (April 2010). Janus Kinase (Jak2)”. Vascular Medicind; Angiolgist http://www.angiologist.com/general-medicine/janus-kinase-2-jak2/ </ref>

As Janus Kinase 2 has a significant role in hematopoiesis, the formation and development of blood cells, mutations in the protein most commonly result in constitutive kinase activation which lead to oncogenesis. Some of the cancers associated with such mutations have been found to be myeloid leukemia, lymphoid leukemia, polycythemia vera, along with other myeloproliferative neoplasms. <ref> Funakoshi-Tago, M., Pelletier, S., & Moritake, H. (2008). Jak2 ferm domain interaction with the erythropoietin receptor regulates jak2 kinase activity. Molecular and Cellular Biology, 28(5), 1792-1801. doi: 10.1128/MCB.01447-07  http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2258779/ </ref> While there are many different genetic mutations which are resultant of leukemias, 85% of patients diagnosed with polycythemia vera are found to have the mutation in their Jak2 protein. <ref> http://www.mayoclinic.com/health/polycythemia-vera/DS00919 </ref>  

There are currently many therapies for differing forms of leukemia, some of which include cytoreductive medications such as hydroxyurea or agrylin, to suppress the bone marrow’s ability to make blood cells, cell destructive medications like cytoxin which act as oral chemotheraputic agents, interferon treatments to stimulate the patient's immune response to fight and kill overproduction or white and red blood cells. Finally traditional chemotherapy is commonly used, as well, for both leukemias as well as progressive polycythemia vera. <ref> http://m.cancer.gov/topics/treatment/bycancer/adultAML/Patient </ref> <ref> http://www.mayoclinic.com/health/chronic-lymphocytic-leukemia/DS00565 </ref> <ref> http://www.mayoclinic.com/health/polycythemia-vera/DS00919 </ref> <ref> Medscape Reference (01, 2012, 10) Polycythemia Treatment and Management. Retrieved from: http://emedicine.medscape.com/article/205114-treatment </ref> While there are a few Jak2 inhibitors already in use which use competitive inhibition for ATP binding pockets, they are not extremely effective due to non-specificity. Due to this issue with specificity, the current therapies for Jak2 mutations are being more focused on allosteric inhibition designs. This research is believed to be hopeful due to the successes it has had with other, different, kinase inhibition. Possible sites which scientists are targeting for such inhibition include, the type II Inhibitor pocket, substrate binding sites, kinase pseudo kinase domain interface, SH2JK2 Linker Region, and the FERM Domain. Currently many of these are in both pre and post clinical trials. <ref> Gnanasambandan, K., & Sayeski, P. (2011). A structure-function perspective of jak2 mutations and implications for alternate drug design strategies: the road not taken. Department of Physiology and Functional Genomics, University of Florida College of Medicine, 18(30), 59-73. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/21864276 http://www.ncbi.nlm.nih.gov/pubmed/21864276 </ref> A brief discussion on diseases associated with Jak2, as well as the function of the protein can be found on an already established Proteopedia page found at [[2b7a]].