The RMCE cassette in TI{TI}Ubx4kb-abx.RMCE has been replaced with sequence encoding the 531bp abxN minimal autoregulatory fragment (this effectively deletes approximately 3.5kb of the 'abxFAIRE' region identified by FAIRE-seq as a broad region of open chromatin in the intronic abx regulatory region). The inserted abxN sequence is not wild type: one of the two clusters of low affinity Ubx-exd protein binding sites in this fragment has been mutated to abrogate binding.