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· DNA binding
· sequence-specific DNA binding transcription factor activity
· signal transducer activity
· ligand-activated sequence-specific DNA binding RNA polymerase II transcription factor activity
· calcium ion binding
· protein binding
· transcription factor binding
· protein kinase binding
· CCR5 chemokine receptor binding
· glucocorticoid receptor binding
· sequence-specific DNA binding
· transcription regulatory region DNA binding
· nucleoplasm
· nucleolus
· cytoplasm
· cytosol
· temperature homeostasis
· eye photoreceptor cell differentiation
· regulation of transcription, DNA-dependent
· regulation of transcription from RNA polymerase II promoter
· protein import into nucleus
· cellular component movement
· acute-phase response
· signal transduction
· JAK-STAT cascade
· nervous system development
· cell proliferation
· virus-host interaction
· cytokine-mediated signaling pathway
· stem cell maintenance
· sexual reproduction
· intracellular receptor signaling pathway
· response to estradiol stimulus
· cellular response to hormone stimulus
· regulation of multicellular organism growth
· response to drug
· glucose homeostasis
· eating behavior
· response to ethanol
· positive regulation of Notch signaling pathway
· positive regulation of transcription, DNA-dependent
· positive regulation of transcription from RNA polymerase II promoter
· neurotrophin TRK receptor signaling pathway
· astrocyte differentiation
· radial glial cell differentiation
· growth hormone receptor signaling pathway
· JAK-STAT cascade involved in growth hormone signaling pathway
信号转导及转录激活蛋白3（英语：Signal transducer and activator of transcription 3，STAT3）是一种由人类基因 编码的转录因子。
STAT3是STAT蛋白家族的成员。受到细胞因子和生长因子的调节，STAT3被受体相关的Janus激酶（JAK）磷酸化，形成同源或异源二聚体，并转移到细胞核，在那里它们起转录激活剂的作用。具体而言，干扰素，表皮生长因子（EGF），白细胞介素（IL-5和IL-6）等配体作用于受体，导致酪氨酸705磷酸化后，STAT3被激活。此外，STAT3可能通过丝裂原活化蛋白激酶（MAPK）和c-src非受体酪氨酸激酶磷酸化丝氨酸727而激活。STAT3介导响应细胞刺激的各种基因的表达，因此在许多细胞过程如细胞生长和细胞凋亡中起关键作用。
当原肠胚形成开始时，STAT3缺陷的小鼠胚胎不能在胚胎发育第7天以后发育。看来在这些发育的早期阶段，STAT3激活是胚胎干细胞（ESC）自我更新所必需的。事实上，如果STAT3通过其他方式被激活，LIF可以被省略，该LIF被提供给小鼠ESC培养物以保持其未分化状态。
STAT3对于TH17辅助性T细胞的分化至关重要，TH17辅助性T细胞已涉及多种自体免疫性疾病。在病毒感染期间，缺乏T细胞中STAT3的小鼠显示产生T-滤泡辅助（Tfh）细胞的能力受损，并且不能维持基于抗体的免疫性。
STAT3能与下列蛋白质发生交互作用：