Figure 1.

A single copy of the MBF-1 activator binding site enhances transgene expression. The M30-tk-CAT transgenes, bearing one, two or three copies of the 30 bp H2A modulator sequence in different location and orientation, were microinjected into sea urchin zygotes. Total RNA from 30 to 50 gastrula stage embryos, microinjected with the indicated transgenes, were hybridized with a ³²P-labelled CAT antisense probe and processed for the RNase protection assay described in ‘Materials and Methods’ section. Asterisk indicates the protected RNA band for the CAT transcript.