Fig. 5. A CEH-20/MAB-5 complex binds the Hox/Hox co-factor site at +5995 in egl-1. (A) Electrophoretic mobility shift assays were performed with epitope-tagged CEH-20 and MAB-5 proteins using wild-type and mutant Site 1 ³²P-labeled oligonucleotides. The mutant oligonucleotide probe contains the NcoI mutation described in Fig. 4C. (B) CEH-20/MAB-5 proteins were used in an in vitro binding reaction with a ³²P-radiolabeled oligonucleotide containing Site 1. Cold competitor oligonucleotide was included in the binding reactions at the indicated molar ratios. The NcoI-Mut, HOX-Mut and CEH-20-Mut mutant probes correspond to those in Fig. 4C.