Serum response factor (SRF) is a transcription factor that binds the serum response element (SRE), a sequence that mediates the transient response of many cellular genes to growth stimulation. SRF is a cardiac-enriched transcription factor that is required for the appearance of beating sarcomeres in the heart. In addition, SRF may also direct the expression of microRNAs that inhibit the expression of cardiac regulatory factors. SRF binding sites are also constitutive promotor elements in many muscle specific promoters. At the c-Fos SRE, formation of a ternary complex containing SRF and its accessory protein p62TCF appears to be important for signal transduction. Two related Ets domain proteins, Elk 1 and SRF accessory protein 1 (SAP 1) have DNA binding properties identical to that of p62TCF
