UASt regulatory sequences drive expression of a mutated form of Spt5 in which six conserved positively charged residues have been mutated to Asp (amino acid substitutions R354D, R405D, K311D, K324D, K319D and R320D). The protein is tagged with Tag:FLAG. Synonymous mutations have been introduced into the sequence so that it is resistant to the Spt5HMS00153 RNAi line.