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. Author manuscript; available in PMC: 2011 Apr 26.
Published in final edited form as: Trends Cell Biol. 2008 Oct 9;18(11):545–551. doi: 10.1016/j.tcb.2008.08.008

Figure 3.

Figure 3

Non-canonical JAK–STAT signaling. In the non-canonical mode of JAK–STAT signaling, unphosphorylated STAT is localized on heterochromatin in association with HP1 in the nucleus. Increasing STAT phosphorylation (by JAK or other tyrosine kinases) reduces the amount of unphosphorylated STAT localized on heterochromatin. This, in turn, leads to HP1 displacement from heterochromatin and heterochromatin instability. Dispersed phospho-STAT binds to cognitive sites in euchromatin to induce target-gene expression. Genes originally localized in heterochromatin are now accessible to STAT or other transcription factors.