UASt regulatory sequences drive expression of spn-F in which all the Ser residues that can be phosphorylated by IKKε have been mutated to Ala (amino acid replacements S53A, S85A, S172A, S202A, S264A, S270A, S349A and S325A), resulting in a phospho-deficient form of spn-F. The protein is tagged with EGFP.