Fig. 3. Su(var)3-7 interacts with itself in the yeast two-hybrid assay. 21 is a fragment of Su(var)3-7 that uses Su(var)3-7 itself as bait in a two-hybrid screening of a Drosophila embryonic cDNA library. A schematic representation of 21 is given above the wild-type protein. A series of Su(var)3-7 deletion constructs have been tested to precisely map the domain of interaction of Su(var)3-7 with itself. /, impossible to test (Delattre et al., 2000); +, interaction with 21; –, no interaction. Grey boxes: zinc fingers; black bars: tryptophan boxes.