Figure 2.

B29 gene 5′ regions act as position- and orientation-independent silencers. Transient transfections to detect transcriptional expression of B29 promoter/silencer region constructs were carried out in the M12 B cell line. The silencer fragments and their position and orientation relative to the B29 minimal (−164) promoter are as indicated. 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.