passages.id: split_4_test_26_passage
passages.type: progene_text
passages.text: The POU domain family of transcription factors was defined following the observation that the products of three mammalian genes , Pit-1 , Oct-1 , and Oct-2 , and the protein encoded by the C. elegans gene unc-86 , shared a region of homology , known as the POU domain .