Fig. 4. UBX binds a cluster of sites important for repression of knot in the haltere. (A) kn^Mel701-1991 sequence as in Fig. 3A, with UBX TAAT core sequences now indicated in brown. Extent of the kn^Mel701-1835 construct, which eliminates a cluster of core UBX sites, is indicated in blue. UBX sites identified by DNaseI footprinting are numbered. (B) Reporter expression directed by kn^Mel701-1835 is observed in both the wing and the haltere. Because the posterior compartment of the haltere is smaller than the anterior compartment, expression of knot at the compartment boundary is shifted with respect to the center of the disc. (C,D) DNaseI footprinting of kn^Mel1599-1991 with purified UBX homeodomain. Lane 1, no UBX protein; lanes 2-6, 3.3-90.0 ng UBX protein; lane 7, G+A sequencing ladder. Four sites protected by UBX are observed. The sequence of UBX site 1 (C) and UBX sites 2-4 (D) are indicated next to the footprints; TAAT core sequences within the each footprint are highlighted.