 Gal4 is a modular protein consisting broadly of a DNA-binding domain and an activation domain.The UAS to which GAL4 binds is CGG-N11-CCG, where N can be any base.Although GAL4 is a yeast protein not normally present in other organisms it has been shown to work as a transcription activator in a variety of organisms such as "Drosophila", and human cells, highlighting that the same mechanisms for gene expression have been conserved over the course of evolution.