Fig. 7. Comparison of hoxb1a and hoxb1b regulatory sequences reveals mutations in defined regulatory elements. Zebrafish genomic sequences lying 5' and 3' of the hoxb1 duplicate genes were produced by the Zebrafish Sequencing Group at the Sanger Institute and can be obtained under Accession Number AL645782 (hoxb1a) and at http://www.sanger.ac.uk/cgi-bin/nph-getblast?humpub/zebrafish_all+dZ227H09 (hoxb1b). (A) Zebrafish hoxb1 gene upstream sequences are compared with the equivalent sequences upstream of mouse and chick Hoxb1 (Pöpperl et al., 1995). The Hox/Pbx-binding sites, repeats 1-3, are indicated in yellow, with changes from the consensus indicated in green. (B) PIPmaker plot (Schwartz et al., 2000) comparing hoxb1a regulatory elements (upper strand) with hoxb1b regulatory elements. There is an AT-rich region of homology lying approximately 4 kb downstream of the translational start site of each gene. These regions do not contain RAREs, or other regulatory elements known to be involved in Hoxb1 regulation. A 5' homology region overlaps the Hox/Pbx-binding repeats (indicated by gray shading).
