Two B or not two B? Overview of the rapidly expanding B-box family of proteins

The B-box gene family represents a large number of genes involved in functi ons such as axial patterning, growth control, differentiation, and transcri ptional regulation. These genes possess several conserved motifs that alway s include a B-box zinc binding motif associated with various other motifs s uch as the RING zinc finger, an alpha -helical coiled-coil, the rfp or B30. 2 motif, propeller domain, and the NHL motif in various combinations. Mutat ions or rearrangements in several B-box family members are associated with human diseases and cancers such as familial Mediterranean fever (FMF), Opit z/BBB syndrome, acute promyelocytic leukemia, mulibrey nanism, and thyroid carcinomas. This suggests that members of this gene family play important r oles in fundamental biological processes. Here we discuss the known members of this rapidly expanding protein family.