FIG. 8.

Promoter activity associated with the IS492 circle junction sequence. (A) The potential promoter sequence created when IS492 ends are joined at the circle junction is indicated by boxes. Relevant regions of plasmids pDV6 and pAG967, used to evaluate circle junction promoter activity, are schematically shown. Arrows and numbers (base pairs) are used to indicate the region of IS492 included on either side of the circle junction on these plasmids. The circle junction sequence is underlined. (B) Promoter activity measured as β-galactosidase activity (Miller units) in plasmids having constitutive control promoters (lacUV5 [pDV5] or conII [pAG620]) or the circle junction and surrounding IS492 sequence (pDV6 or pAG967). Besides having different amounts of surrounding IS492 sequence, pDV6 and pAG967 have different copy numbers (multiple and single copy, respectively). The relative β-galactosidase activities for these promoter constructions remained constant in multiple experiments.