Figure 5.

Site-directed mutagenesis of the TOAD and FROG motifs disrupts silencing activity. Transient transfections to detect transcriptional expression of deletion constructs −354 and −565 with introduced point mutations in the TOAD and FROG motifs, respectively, were carried out in the M12 B cell line. Mutagenized nucleotides are indicated by underlined lowercase type. The activity of each construct is expressed as a percentage of the CAT activity obtained with the B29 minimal (−164) promoter construct (100%). Deletion constructs −164, −354, and −565 are identified by nucleotide numbers with respect to the major start site of transcription (+1) and are shown for comparison.