UASp regulatory sequences are fused upstream of a FRT cassette containing the His2B coding region tagged with GFP. The cassette is followed by the His2B coding region tagged with the mKO fluorescent protein.
In the absence of Scer\FRT, the T:Avic\GFP-tagged His2B coding region in P{UASp(FRT.His2B-GFP)His2B-mKO} is expressed under the control of the UASp sequences and there is little expression of the T:Zzzz\KOmKO-tagged His2B coding region which is downstream of the Scer\FRT cassette. In the presence of Scer\FRT, the Scer\FRT cassette containing the T:Avic\GFP-tagged His2B coding region is excised, allowing expression of the T:Zzzz\KOmKO-tagged His2B coding region under the control of the UASp sequences. This dual-colour method can be used to differentially label "old" versus "new" histones in cells.
In the absence of Scer\FRT, the T:Avic\GFP-tagged His2B coding region in P{UASp(FRT.His2B-GFP)His2B-mKO} is expressed under the control of the UASp sequences and there is little expression of the T:Zzzz\KOmKO-tagged His2B coding region which is downstream of the Scer\FRT cassette. In the presence of Scer\FRT, the Scer\FRT cassette containing the T:Avic\GFP-tagged His2B coding region is excised, allowing expression of the T:Zzzz\KOmKO-tagged His2B coding region under the control of the UASp sequences. This dual-colour method can be used to differentially label "old" versus "new" histones in cells.