cAMP stimulates the C/EBP-related transcription factor rNFIL-6 to trans-locate to the nucleus and induce c-fos transcription.

The c-fos serum response element (SRE) is a multifunctional regulatory region of the c-fos promoter that responds to a variety of inducers. Recently, we have demonstrated that the SRE binds the C/EBP-related transcription factor rat NFIL-6 (rNFIL-6). In this study we show that rNFIL-6 is regulated by the cAMP second messenger pathway in the rat pheochromocytoma PC12 cell line. Following forskolin treatment, rNFIL-6 binding to the SRE is increased, and the factor becomes phosphorylated and undergoes a trans-location to the nucleus. In transient cotransfection assays, rNFIL-6 is capable of trans-activating the c-fos promoter in a manner dependent on the SRE. These data show that rNFIL-6 undergoes a novel activation in which cAMP-induced nuclear trans-location allows rNFIL-6 to bind to the SRE and contribute to c-fos activation. We propose that rNFIL-6 is an additional regulatory component of the c-fos gene, which provides cAMP responsiveness to the multifunctional SRE.