BST2 transcripts and promoter activity in AMkL cell lines; gel shifts with the +39/+65 BST2 probe. (A) Transcript levels of BST2 in the DS AMkL cell line, CMK, and non-DS AMkL cell line, Meg-01 (top panel), measured by real-time PCR, and BST2 promoter activities in CMK and Meg-01 cells (bottom panel), measured by relative luciferase activity following transient transfection of the cell lines with the BST2 reporter gene construct, pGL3B-BST2pro. Error bars indicate standard error of measurement of 3 independent experiments. (B) Gel shift assays were performed with CMK and Meg-01 nuclear extracts and the ³²P-labeled +39/+65 BST2 oligonucleotide probe in the absence and presence of 100-fold molar excess commercial consensus GATA1 oligonucleotide. The specific DNA/protein complexes are indicated by lowercase letters. For the supershifts, GATA1 antibodies were added to the reaction mixtures and incubated for 30 minutes prior to separating the DNA/protein complexes. (C) In vivo binding of the long- and short-form GATA1 proteins to the BST2 promoter was confirmed by ChIP assays, as described in “Materials and methods.”