Interaction of GRP94 with FAC by yeast two-hybrid analysis. (A) Structure of full-length FAC and carboxy-terminal truncated mutants (amino acid residues are residues indicated) and (B) an in-frame protein product of the IVS4+4 mutation that deletes exon 4 sequences were fused in-frame, downstream of the DNA-binding domain of GAL4 in the vector pGBT or pBDGAL4Cam. Transcriptional activation ofLacZ in yeast transformed with these constructs as well as with pACT-GRP94 that contains the entire coding region of human GRP94 fused to the GAL4 transcriptional activation domain was assessed by a filter color assay. The rapidity and intensity of color development was scored by visual inspection as shown: −, white color after 12 hours; +, blue color after 1 to 12 hours; ++, dark blue color or blue color after less than 1 hour.