The QF2w 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. In addition, the activation domain has been mutated to reduce activity, by altering the charge on the C-terminus. The QA-1F DNA-binding domain binds specifically to the QUAS DNA sequence and thus QUAS and QF2w 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 QF2w driver. QF2w is optimal for broad expression patterns or strong promoters, whereas the related QF2 driver is best suited when strong transcriptional activation is required in a subset of cells. Since the QF2w 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).