FIG. 5.

Trimeric Hoxb1-Pbx1-Meis1 DNA binding complexes preferentially bind to a subportion of the Hoxb1 ARE that contains consensus Meis and Pbx-Hox sites. EMSA was performed on DNA binding complexes containing various combinations of Pbx1, Meis1, or Hoxb1 proteins (indicated above the gel lanes). The DNA probes consisted of radiolabeled oligonucleotides containing subfragments of the Hoxb1 ARE (32), indicated schematically at the top. r1 to r3 were previously identified by their similarity to the Pbx consensus site. Migrations of dimer and trimer complexes are indicated to the left. Arrow heads denote trimeric complexes. Free DNA probes are not shown in the middle panels because they are smaller and migrate faster than the full-length ARE. The probe used in the rightmost panel consisted of a multimerized Pbx-Hox site from the Hoxb2 r4 enhancer (20).