14-3-3 sigma, also known as Stratifin (SFN), belong to the 14-3-3 family. The 14-3-3 family of proteins plays a key regulatory role in signal transduction, checkpoint control, apoptotic and nutrient-sensing pathways. 14-3-3 proteins are highly conserved and ubiquitously expressed. There are at least seven isoforms, beta, gamma, epsilon, sigma, zeta, tau and eta that have been identified in mammals. 14-3-3 sigma was identified as an epithelial cell marker and appeared to function as a tumor suppressor whose expression can be down regulated via methylation. Loss of 14-3-3 sigma expression results in a defective G2/M phase checkpoint and appears to contribute to both epithelial and non-epithelial tumorigenesis. Recombinant human 14-3-3 sigma was expressed in E. coli and purified by using conventional chromatography techniques.