FIGURE 1.

Interaction of syndecan cytoplasmic C2 region with β4 integrin cytoplasmic domain in a yeast two-hybrid assay. A, yeast strain AH109 was transformed with p53 (Gal4-binding domain bait vector) and T-antigen (Gal4 activation domain prey vector as a positive control) or with Lamin C (bait) and T antigen (prey) or empty vector (bait) and β4 integrin sequence encoding amino acids 1473–1752 (prey) as negative controls. The yeast were spread on SD-leu-trp-his-ade plates containing x-α-gal to visualize positive (blue) colonies. B and C, the β4 fragment (prey) was transformed into yeast with bait vector containing the cytoplasmic domains of either Sdc1, Sdc2, Sdc3, or Sdc4 (B) or Sdc1 lacking its C1 and C2 regions (Sdc1ΔC1/C2), its C1 region (Sdc1ΔC1), or its C2 region (Sdc1ΔC2) (C). D, quantification of data shown in A–C. After 9 days, the number of blue transformants growing on the SD-leu-trp-his-ade plates was counted and divided by the total number of transformants grown on SD-leu-trp plates to calculate the percentage of colonies with positive interactions. All percentages represent the average percentage of three independent transformations. Any strain with a percentage greater than 2% is shown by a plus sign in the β4 interaction column. No positive colonies were obtained for syndecan fragments co-transformed with a plasmid bearing empty prey vector. The syndecan cytoplasmic domains are depicted containing the conserved region 1 (C1), variable region (V), and conserved region 2 (C2) and expressed as a fusion with the Gal-4-binding domain. E, schematic diagram showing the α6β4 integrin and its transmembrane (TM) region, FNIII repeats I–IV, and cytoplasmic tyrosines. The region containing the syndecan binding site (amino acids 1473–1752) identified by yeast two-hybrid analysis is shown.