In addition to measuring transcription in vitro or in transient transfection assays, an alternative method to study the function of transcription factors is to inject reporter DNA together with either nuclear extract or factor gene into Xenopus oocytes. Here we introduce the GAL4-derived assay, which was established in other systems, to study transcriptional activation in the frog oocyte. In our experiment, purified recombinant transactivator fusion protein GAL-VP16(40N) was coinjected with a beta -globin reporter gene into the Xenopus oocytes nucleus (germinal vesicle). The reporter promoter contained five GAL4 binding sites upstream of an octamer motif. Xenopus oocytes were prepared as described previously.