Members of the Pax family of transcription factors contain a paired box DNA binding domain and may or may not contain a paired-type homeodomain and/or octapeptide region. Nine Pax genes have been identified in mammals and are divided into four subgroups based on the sequence elements present. Pax genes play a variety of roles during embryogenesis, regulating cell-lineage specification, proliferation, migration, and survival of diverse cell and tissue types. Several of the Pax genes are also expressed in cancers and serve as tumor markers.
Pax5, also known as BSAP (B-cell-specific transcription factor) is a 42 kDa protein belonging to the paired box transcription factor family. It is a developmental regulator that is important for B-cell lineage commitment and development. Human Pax5 is a 391 amino acid (aa) protein containing the paired DNA-binding domain at the N-terminal region. Several alternatively spliced isoforms with altered C-terminal regions and possessing different transactivation properties have been described. All isoforms share the N-terminal 235 aa with full-length Pax5. Human Pax5 shares 99%, 97%, and 94% aa sequence identity with mouse, bovine, and canine Pax5, respectively.