Stat3 is present in the developing and adult rat cerebellum and participates in the formation of transcription complexes binding DNA at the sis-inducible element.

Stat3 is a member of a recently identified family of proteins named STATs for their ability to act as signal transducers and activators of transcription. Stimulation of epidermal growth factor or cytokine receptors can cause activation of Stat3 and transduction of specific responses to the nucleus. Here the presence of Stat3 has been examined in the rat cerebellum at different times during postnatal development and adulthood by means of immunohistochemistry and western blotting. In addition, DNA binding activity at the sis-inducible element that is present in the promoter of the c-fos gene has been studied by electrophoretic mobility shift assay. The results have shown that Stat3 p92 is abundant in the rat cerebellum. Stat3 was found in the external granule cell layer and also within the molecular layer from postnatal day (P) 0 to P7. From P15 to the adult, the internal granule cell layer and Purkinje cells were also stained for Stat3. Nuclear extracts were found to contain DNA binding activity to the sis-inducible element during development and adulthood. Supershift assays demonstrated that Stat3 mediates the formation of one protein-DNA complex. The present results suggest that Stat3 participates in intracellular signaling and is involved in maintaining basal c-fos expression in the cerebellum of the developing and adult rat under physiological conditions.