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Merging Absolute and Relative Quantitative PCR Data to Quantify STAT3 Splice Variant Transcripts
Published on: October 9, 2016
Extracellular signal-dependent nuclear import of STAT3 is mediated by various importin alphas
Ryosuke Ushijima1, Naoko Sakaguchi, Arihiro Kano
1Department of Bioengineering, Graduate School of Engineering, Osaka City University, Osaka 558-8585, Japan.
Abstract:
The signal transducer and activator of transcription 3 (STAT3) is a transcription factor that is involved in a variety of biological functions. STAT3 is activated by cytokines and growth factors via the phosphorylation of a tyrosine residue, dimerization, and subsequent nuclear translocation. However, the mechanism of its nuclear translocation is unclear. A study of the cytokine-stimulated import of STAT3 into the nucleus is reported herein. An oncostatin M (OSM)-dependent nuclear import assay system was first established in living cells. Using this system, we demonstrated that the microinjection of the importin alpha5/NPI-1 mutant, an anti-importin beta antibody, and the RanQ69L mutant inhibited the nuclear import of STAT3. Second, we showed that tyrosine-phosphorylated STAT3 associates, not only with importin alpha5/NPI-1 but also with other importin alphas, as a result of OSM stimulation, as evidenced by a solution binding assay. These findings suggest that the extracellular signal-dependent nuclear transport of STAT3 is mediated by various importin alphas, importin beta, and Ran.
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