PAX5 (D7H5X) XP^® Rabbit mAb (Alexa Fluor^® 647 Conjugate) #48505

Paired box (PAX) proteins are a family of transcription factors that play important and diverse roles in animal development (1). Nine PAX proteins (PAX1-9) have been described in humans and other mammals. They are defined by the presence of an amino-terminal "paired" domain, consisting of two helix-turn-helix motifs, with DNA binding activity (2). PAX proteins are classified into four structurally distinct subgroups (I-IV) based on the absence or presence of a carboxy-terminal homeodomain and a central octapeptide region. Subgroup I (PAX1 and 9) contains the octapeptide but lacks the homeodomain; subgroup II (PAX2, 5, and 8) contains the octapeptide and a truncated homeodomain; subgroup III (PAX3 and 7) contains the octapeptide and a complete homeodomain; and subgroup IV (PAX4 and 6) contains a complete homeodomain but lacks the octapeptide region (2). PAX proteins play critically important roles in development by regulating transcriptional networks responsible for embryonic patterning and organogenesis (3); a subset of PAX proteins also maintain functional importance during postnatal development (4). Research studies have implicated genetic mutations that result in aberrant expression of PAX genes in a number of cancer subtypes (1-3), with members of subgroups II and III identified as potential mediators of tumor progression (2).
PAX5, also known as B cell-specific activator protein (BSAP), was originally identified as a DNA-binding protein with affinity for both immunoglobulin heavy-chain and kappa light-chain loci (5). PAX5 is unique within the PAX family in being the only member with reported expression in the hematopoietic system. PAX5 is required to promote differentiation of common lymphoid progenitors (CLPs) into B cells (5,6); it is also required for the continued maintenance of B cell identity following differentiation (7). Disruptions to the expression of PAX5 have consequently been linked with lymphoid cancer development (8).