In a cell free system , the affinity of binding of a DNA fragment ( 737 715 ) containing a PPRE from __SP__ __NODE__ gene and a heterodimeric protein protein complex consisting of hamster __NODE__ and of __SP__ __NODE__ is the same as the affinity of binding of a DNA fragment ( 575 548 ) containing a PPRE from __SP__ __NODE__ gene and a heterodimeric protein protein complex consisting of hamster __NODE__ and of __SP__ __NODE__ .