Alignment of promoter regions of mass 18,893-associated loci. The alignment ends immediately prior to the predicted common transcriptional start site of Mup loci. The first underlined region indicates a C/A substitution followed by an additional 13 A residues present in B6 gene 17. Similar though non-identical A-rich regions are found in the equivalent location at each Mup loci. The second underlined region is the TATA-box sequence, common to all Mup loci.