Members of Oct family of transcription factors specifically interact with Octamer motif ATGCAAAT, a regulatory element important for tissue- and cell-specific transcription as well as for transcription of a number of housekeeping genes. All of the members of the Oct family contain two highly conserved domains which are separated by 14-26 variable amino acids. These include the POU homeodomain and the POU-specific domain. Both are required for DNA binding and are involved in protein-protein interactions. Evidences indicate that regulation of Oct family transcription factors occurs at the level of phosphorylation. Oct4 is renowned as a transcription factor expressed by undifferentiated embryonic stem cells and embryonic germ cells.