Fig. 3. The Clathrin-binding and J domains of Auxilin are sufficient and the J domain is necessary for Delta signaling. (A) Drosophila Auxilin (1165 amino acids) and four transgene constructs. To the right is a summary of the complementation test results. UAS, UAS-cDNA; gDNA, genomic DNA-based constructs; +, indicates complementation of all aux- mutant phenotypes including lethality (rescue); -, indicates no activity (no rescue). The aux- genotypes tested for complementation are aux⁷²⁷/aux^D128 (strong) and aux^K47/aux^D128 (hypomorphic). Three independent UAS-auxilin^J lines were tested, and in an aux⁷²⁷/+ background, two lines showed aux mutant-like wing and eye phenotypes (data not shown) indicative of dominant-negative activity. No auxilin^K+PTEN lines are dominant negative. The auxilin^J line tested for complementation expresses protein; it has dominant-negative activity and protein is detected in immunolabeled eye discs (data not shown). (B) Confocal images of a facet (diagram of cell outlines at far right) in wild-type third instar larval eye disc immunolabeled with anti-Auxilin antibodies and phalloidin (F-actin).