Krueppel-like factor 4 (KLF4) is a zinc finger transcriptional regulator that has been identified as a good indicator of stem cell-like capacity and is subsequently used in iPS cell generation. KFL4 plays an important role in maintaining stem cells, and in preventing their differentiation. 

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).