A cis-element mediating Ultrabithorax autoregulation in the central nervous system.

We dissected an upstream control region (a BXD fragment) from the homeotic gene Ultrabithorax (Ubx) of Drosophila which confers a Ubx-like expression pattern in the embryonic ectoderm. We found several distinct enhancer elements spread through the whole BXD fragment each of which is active in transformed embryos, mediating a different pattern of beta-galactosidase expression in the ventral nerve cord. The strongest of these patterns mimics Ubx expression within the Ubx domain. This pattern is strictly dependent on Ubx function. Thus, the BXD control region contains a Ubx response element, suggesting that positive autoregulation of Ubx may occur in the central nervous system of the developing embryo.