FIG. 1.

Deletion alleles of the ddb-1, cul-4, and skpt-1 genes and two-hybrid interaction between DDB-1 and CUL-4. (A to C) Line drawings of the ddb-1, cul-4, and skpt-1 genomic regions on chromosomes IV, II, and III, respectively. Exons are represented as boxes and shaded areas represent coding regions. Arrows indicate the start point and direction of translation. Broken boxes with diagonal shading indicate the nearest exon of the closest upstream gene. Regions deleted in mutant alleles are represented below the gene as the missing regions bounded by dashed lines. The ddb-1(tm1769) allele is a 540-bp deletion that removes 177 bp of the promoter region and the complete exons 1 and 2 (A). The cul-4(gk434) allele is a 580-bp deletion that removes 305 bp of the promoter region and the complete exons 1 and 2 (B). The skpt-1(ok851) allele is a 698-bp deletion that removes the last 41 bp of exon 1, the complete exons 2 and 3, and the first 117 bp of exon 4 (C). The scale bar is 1 kilobase. (D) DDB-1 specifically binds to CUL-4. The interactions between DDB-1 and the six C. elegans cullins (CUL-1 through CUL-6) were examined in the two-hybrid system using the yeast strain pJ69-4A, which enables selection for growth on histidine- or adenine-deficient medium. DDB-1 was fused to the GAL4 activation domain, and the cullins were fused to the GAL4 DNA binding domain.