HOMODIMERIZATION AND INTERMOLECULAR TYROSINE PHOSPHORYLATION OF THE TYK-2 TYROSINE KINASE

The Jak kinases and Stat transcription factors play a major role in si gnaling of various cytokines including IFN alpha. In this report we sh ow a ligand-independent interaction between Tyk-2 and Jak-1 kinases. W e also demonstrate that the Tyk-2 kinase forms a homodimer that has th e ability to undergo intermolecular tyrosine phosphorylation. The form ation of the Tyk-2 homodimer is independent of both tyrosine phosphory lation and the presence of the tyrosine kinase domain.