| Summary |
Restriction endonuclease mapping. Southern hybridization, and DNA sequence analyses of a 12.8 kb bacteriophage X EMBL-3 genomic clone from Morone saxatilis (striped bass) provided evidence for the existence of two Hox genes. The coding regions of these two Hox genes, in comparison to those of other vertebrates, had a distinct signature that was most related to the Hox B5 and B6 genes. The genomic organization of the Hox B5-B6 region in Morone is relatively similar to that of other vertebrates, with the exception of the intergenic length, which is approximately half that of other species (1.2 kb). The upstream regions of the Hox B5 and B6 genes from Morone share significant sequence similarity with known promoters in the mouse and zebrafish. Comparative DNA sequence analysis of the Morone Hox B5 and B6 gene promoters to those from previously characterized Hox gene promoters revealed a serum response element, 10 base pair boxes. Retinoic Acid Response Elements (RARE's), and caudal binding sites. A search for repeat structures identified a series of eight contiguously arranged direct repeats, that can be divided into two matching quartets, which provided evidence for an intra-cluster duplication event within the Morone saxatilis Hox B cluster. A comparison of the Hox B5-B6 region of Morone to the paralogous region on the Hox A revealed several short interspersed regions of relatedness between these two paralogous regions. These results demonstrate that the Hox B5-B6 region from Morone saxatilis has diverged significantly from orthologous regions among other vertebrate species. However, the Hox B5-B6 exon-coding regions and specific promoter elements have been highly conserved among evolutionarily divergent vertebrates. |
