The GAVPO driver is a light-activated transcriptional activator ('driver') designed for use in the 'LightOn' binary expression system. It is a fusion protein composed of amino acids 1-65 of the Saccharomyces cerevisiae GAL4 gene ( SGDID:S000006169 ) (this fragment contains the DNA-recognition element but not the dimerization domain), VVD (the small light-oxygen-voltage (LOV) domain-containing protein encoded by the Neurospora crassa Vivid gene, UniProtKB:Q9C3Y6) and the transcriptional activation domain from the Homo sapiens 'p65' gene (RELA, HGNC:9955). Upon illumination with blue light, the presence of the LOV domain results in dimerization of the GAVPO protein; this dimer can bind to the UAS regulatory sequence, resulting in transcriptional activation of a downstream gene. The light-activated GAVPO dimer has a half life of 2 hours. In GAVPO, the VVD domain contains two amino acid substitutions (N56K and C71V); these mutations enhance dimerization and decrease background expression in the dark (PMID:22327833).