| Cellular localization | Cytoplasm. Nucleus. Shuttles between   the nucleus and the cytoplasm. Constitutive nuclear presence is independent   of tyrosine phosphorylation. Predominantly present in the cytoplasm without   stimuli. Upon leukemia inhibitory factor (LIF) stimulation, accumulates in   the nucleus. The complex composed of BART and ARL2 plays an important role in   the nuclear translocation and retention of STAT3 |