Fig. 4. Western blot of B42 AD-fused prey proteins that are imported into the nucleus of the yeast three-hybrid cells. Nuclear proteins were extracted from L40uraMS2 cells that contained the bI4 intron–MS2 hybrid bait RNA and either the full-length LeuRS (right) or the smallest CP1 (F2–R1)-containing LeuRS fragment (left), which were fused to B42 AD as prey. These prey proteins also contain a 14 amino acid V5 epitope that could be detected using an anti-V5 antibody. Protein markers (data not shown) were used to identify the prey proteins based on molecular weight. The CP1 (F2–R1)–B42 AD fusion is shown in the left lane at ∼36 kDa, while the full-length LeuRS–B42 AD fusion is in the right lane at ∼112 kDa.