POU family

POU (pronounced 'pow') is a family of proteins that have well-conserved homeodomains.

Etymology
The acronym POU is derived from the names of three mammalian transcription factors:
 * the Pituitary-specific Pit-1
 * the Octamer transcription factor proteins Oct-1 and Oct-2 (octamer sequence is ATGCAAAT)
 * the neural Unc-86 transcription factor from Caenorhabditis elegans.

Diversity
POU domain genes have been described in organisms as divergent as Caenorhabditis elegans, Drosophila, Xenopus, zebrafish and human but have not been yet identified in plants and fungi.

There is a surprisingly high degree of amino acid sequence conservation (37%-42%) of POU homeodomains to the transcriptional regulator comS from the gram positive prokaryote Bacillus subtilis. Interestingly, akin to the way that POU homeodomain regulators lead to tissue differentiation in metazoans, this transcription factor is critical for differentiation of a subpopulation of B. subtilis into a state of genetic competence.