Binding of the transcription factor, GATA-2, to the −24 GATA element of the PECAM-1 promoter. Nuclear extracts derived from DAMI cells were incubated with a 32P-labeled double-stranded oligonucleotide containing either a GATA consensus binding site (lanes 2 to 5) or a mutated CTTT sequence in its place (lanes 6 and 7). Competition reactions were performed using a 100-fold molar excess of unlabeled double-stranded oligonucleotide containing either the wild-type (lane 3) or mutant CTTT sequence (lane 7). Immunodepletion studies (lanes 4 and 5) were conducted by preincubating the nuclear extracts with 1 μg of a monoclonal antibody specific for either GATA-1 (lane 4) or GATA-2 (lane 5). Note that a GATA-2-specific DNA-protein complex (arrow) forms only when the GATA sequence is present. Comparable results were obtained using nuclear extracts derived from HEL cells (data not shown).
