SRY (sex determining region Y)-box 2 (SOX2) is a transcription factor critical for maintaining the self-renewal capacity of undifferentiated stem cells. Ectopic expression of SOX2 has been used to produce iPS cells in culture. 

Human elongation factor-1 alpha (EF-1 alpha) is a constitutive promoter of human origin that can be used to drive ectopic gene expression in various in vitro and in vivo contexts. EF-1 alpha (or EF1a) is often useful in conditions where other promoters (such as CMV) have diminished activity or have been silenced (as in embryonic stem cells).