SRF Serum response factor (SRF) is a transcription factor that plays a key role in the transduction of mechanical signals from cytoplasmic actin and the extracellular environment, to the cell nucleus. It is highly conserved from yeast to humans and plays a role in a large number of mechanotransduction pathways. It has been estimated that the transcription of as many as 300 genes is under the control of SRF signalling, and of these, more than 200 are directly targeted by the protein.