Transcriptional activity of mHS–25 and hHS+14 in the neo^r activation assay. (A) Fragments containing mHS–25, hHS+14, and mHS–3.5 were inserted either in the forward (F) or reverse (R) orientation into the neo^r-gene–containing vector, pMC1neo(polyA). The fold change in the number of G418-resistant colonies relative to the baseline vector, pMC1neo(polyA), upon transfection of L929 cells (□) and MEL cells (▪) is shown for each construct. Each bar represents average colony number from 5 experiments with each construct. Error bars (1 SD) are shown. Absolute average numbers of colonies were 14.3 colonies/1 × 10⁷ L929 cells and 8.2 colonies/2 × 10⁷ MEL cells when 20 μg linearized pMC1neo(polyA) was transfected. The amount of each recombinant plasmid DNA used for transfection was adjusted to ensure that equal molar ratios were transfected. (B) Sequence of mHS–25 and hHS+14. Sequence of GATA sites are marked in bold and E-boxes, in italics and bold.