passages.id: split_4_test_712_passage
passages.type: progene_text
passages.text: The t ( 1 ; 19 ) chromosomal translocation of pediatric pre - B cell leukemia produces chimeric oncoprotein E2a - Pbx1 , which contains the N - terminal transactivation domain of the basic helix - loop - helix ( bHLH ) transcription factor , E2a , joined to the majority of the homeodomain protein , Pbx1 .