The p65(AD)::pMagFast1 entry in FlyBase represents a hemidriver that contains the transcriptional activation domain from the Homo sapiens 'p65' gene (RELA, HGNC:9955) fused to 'pMagFast1', a positively charged engineered domain that can heterodimerize with a compatible negatively charged 'nMag'-type domain upon stimulation with blue light (for details of pMagFast1 see PMID:25708714). p65(AD)::pMagFast1 forms one half of the 'ShineGAL4' split-GAL4 system: when combined in vivo with a hemidriver containing a DNA-binding domain fused to a compatible nMag-type domain and exposed to blue light, the light-induced interaction between the nMag/pMag pair can reconstitute a functional transcriptional activator that can drive transcription of a downstream gene of interest. The DNA-binding specificity of the reconstituted transcriptional activator will depend upon the DNA-binding domain present in the nMag-type domain containing hemidriver. Since transcription is only activated at the intersection of the expression patterns of the two hemidrivers and upon activation by light, the ShineGAL4 system can be used to drive expression in a restricted pattern (FBrf0252177). The exact sequence of the p65(AD)::pMagFast1 hemidriver may differ depending on the particular transgene or modified endogenous locus being used. In particular, the number of copies of the pMagFast1 domain may vary, altering the strength of interaction with a compatible nMag-containing hemidriver in the presence of blue light.