passages.id: split_1_test_2003_passage
passages.type: progene_text
passages.text: Given that these promoters showed no structural or functional homology with the previously characterized rat beta4 subunit promoter ( Bigger , C. B. , Casanova , E. A. , and Gardner , P. D. ( 1996 ) J. Biol. Chem. 271 , 32842 - - 32848 ) except for the involvement of an Sp1 binding element , we propose that constitutive expression of the beta4 subunit gene in these three close species may be controlled by the general transcription factor Sp1 .