PLU-1 (JARID1B) and the other three members of this subfamily varies more than is typical within subfamilies in the Loop 2 and Helix 5 region of the ARID sequence (see Figure 1). PLU-1 has a histidine within the Helix 5 region at a position where the other members of this subfamily contain a leucine. This region is the major groove interaction site in other ARID members and could be expected to play an important role in sequence recognition. Second, PLU-1 is expressed in a highly tissue restricted manner in contrast to other JARID1 members, which are broadly expressed [reviewed in (1)]. RBP2 (JARID1A) was chosen to represent the more typical members of this subfamily. As shown in Figure 4, both RBP2 (JARID1A) and PLU-1 (JARID1B) bind DNA with little or no discernible sequence specificity.
