The FRT cassette present in P{His3.3B(FRT.His3.3B.WT.FLAG.ubiGFP)His3.3B.H3.2.HA} has been excised (removing wild-type His3.3B sequences present within the cassette), allowing the mutated form of His3.3B (which contains the amino acid replacements S31A, A87S, I89V and G90M and which is also tagged at the C-terminal end with Tag:HA) to be expressed under the control of the His3.3B promoter.
His3.3BH3.2.Tag:HA does not rescue the sterility of His3.3AKO His3.3BKO double homozygous males.