The QF2 entry in FlyBase represents an artificial transcriptional activator ('driver') derived from Neurospora crassa QA-1F (UniProtKB:P11638). It contains the QA-1F DNA-binding and transcriptional activation domains, but the middle domain has been deleted. This results in dramatically lower toxicity in transgenic Drosophila compared to a QF driver encoding the complete QA-1F protein. The QA-1F DNA-binding domain binds specifically to the QUAS DNA sequence and thus QUAS and QF2 form a binary expression system that can be used to control the spatial and temporal expression of a gene of interest: a transgene or modified endogenous locus carrying the target gene of interest downstream of QUAS sequences is combined with a second transgene or modified endogenous locus encoding the QF2 driver. QF2 is best suited when strong transcriptional activation is required in a subset of cells, whereas the related QF2w driver is optimal for broad expression patterns or strong promoters. Since the QF2 driver includes the target of the QS repressor (the QA-1F activation domain), it can be suppressed by QS, providing a further level of regulation (FBrf0227669).