Promoterless mutated form of His3.3B (amino acid replacements S31A, A87S, I89V and G90M), which is tagged at the C-terminal end with Tag:HA and followed by His3.3B 3' UTR sequences. The FRT cassette which is present in P{His3.3B(FRT.His3.3B.WT.FLAG.ubiGFP)His3.3B.H3.2.HA} prevents expression of this mutated form of His3.3B.