Regulation and function of signal transducer and activator of transcription 3

Figure 1 Domain structure of signal transducer and activator of transcription (3α and 3β). The signal transducer and activator of transcription 3α (STAT3α) protein is composed of N-terminal, coiled-coil, DNA binding, linker, SH2, and transactivation domains. However, the transactivation domain is absent in the alternative splicing variant, STAT3β.

Figure 2 Converging roles of signal transducer and activator of transcription 3. Different signals can selectively trigger signal transducer and activator of transcription 3 phosphorylation. Tyr-phosphorylated STAT3 translocates into the nucleus and regulates gene expression, thus playing an important role in cell proliferation, tumorigenesis, self-renewal and pluripotency. On the other hand, Ser-phosphorylated STAT3 translocates into mitochondria, binds with the complexes in respiratory chain, and ultimately maintains the cellular respiration and mitochondrial protection. MAPK: Mitogen-activated protein kinase; ROS: Reactive oxygen species; JNK: c-Jun N-terminal kinase; JAK: Janus kinase.