Fig 4.
Zα by itself activates transcription of the reporter. Expression of Zα alone without the Gal4 AD was examined. pGNA-Zα expresses Zα with the simian virus 40 T-antigen nuclear localization signal at the N terminus (described in Materials and Methods). (A) Experiments were performed with different pLacZcOp-(dC-dG)n reporters. hZαADAR expression increases β-galactosidase activity significantly as stretches of dC-dG become longer. Activation on X-gal plates of the reporter gene LacZ by the pGNA plasmid alone or expressing various proteins; pGNA-Zβ, pGNA-Zα, and pGNA-Zaa in pLacZcOp-(dC-dG)n or pLacZcSm-(dC-dG)n when n = 5 (B) or n = 9 (C). The contribution of negative supercoiling to Z-DNA formation because of opposite or same orientations is apparent in B, where n = 5. The great tendency of longer stretches to form Z-DNA where n = 9 swamps out the smaller distinction between opposite and same orientation.