Figure 1

SpCBFβ structure and heterodimerization with SpRunt-1. (A) Alignment of CBFβ sequences from S. purpuratus (Sp) zebrafish (Dr), Homo sapiens (Hs, variant 2 of the two mammalian splice variants), mouse (Mm, variant 1 of the two mammalian splice variants), Drosophila (two genes, DmBro and DmBgb), and C. elegans. Amino acid residues that are identical between SpCBFβ and at least one other homologue are highlighted in black, and conserved substitutions are highlighted in grey. Amino acid pairs of which the respective codons are separated by introns in each gene are underlined; the four introns conserved between urchin and vertebrates are indicated by arrowheads. (B) EMSA analysis using recombinant Runt domain (RD) or full-length SpRunt-1 (FL) either alone or in the presence of recombinant SpCBFβ. Note that the full-length SpRunt-1 does not bind DNA very effectively by itself, suggesting the presence of domains that inhibit DNA binding within the full length protein. SpCBFβ complexes with both the Runt domain and full-length SpRunt-1, as indicated by a “supershift”, but does not bind DNA by itself. (C) Immunoblot of SpCBFβ from nuclear extract (NE), and nuclear extract immundepleted (ID) and immunoprecipitated (IP) with anti-SpRunt-1 or nonspecific IgG. Molecular weight markers (in kilodaltons) are shown on the right.