Motifs differ in their intrinsic biases toward the generation of promoter versus enhancer activities. (A, top) Sequence design for tandem repeats of 32 motifs, each totaling 87 bp in length; (bottom) enhancer and promoter activities of motif tandem repeats. (B, top) Sequence design for spaced motif repeats, with 18 motifs and three spacer sequences, each totaling 87 bp in length; (bottom) enhancer and promoter activities of spaced motif sequences. The log₂ of enhancer activity is shown. Stars indicate at least twofold activity with significance in a one-sided Student's t-test (P < 0.05). Error bars are SEM of n = 3 biological replicates. Promoter and enhancer activities are defined as in Figure 2B.