UASt regulatory sequences drive expression of spn-F in which all the Ser residues that can be phosphorylated by IKKε have been mutated to Asp (amino acid replacements S53D, S85D, S172D, S202D, S264D, S270D, S349D and S325D), resulting in a phosphomimetic form of spn-F. The protein is tagged with EGFP.