The specific binding of the erythroid GATA1 factor to the rs311103[G] DNA fragment. (A) Nuclear extracts were prepared from HEK293T cells (HEK N.E.) transfected with expression vectors for GATA1 or GATA2 or with the empty pCMV6 vector (V). These were then incubated with 1 ng of ³²P-labeled 22-bp rs311103[G] or rs311103[C] DNA fragment with and without the addition of antibody (Ab) against GATA1 or GATA2 (left panel). The shifted and supershifted bands are indicated with asterisks (right panel). Unlabeled rs311103[G] or rs311103[C] DNA fragments (10, 20, or 40 ng) were added to compete with the ³²P-labeled rs311103[G] fragment (right panel). (B) Binding of endogenous GATA1 factor to the rs311103[G] DNA fragment. Nuclear extracts prepared from native K-562 cells (K-562 N.E.) were used.