Transcription factor that plays an essential role in commitment of lymphoid progenitors to the B-lymphocyte lineage (PubMed:10811620, PubMed:27181361). Fulfills a dual role by repressing B-lineage inappropriate genes and simultaneously activating B-lineage- specific genes (PubMed:10811620, PubMed:27181361). In turn, regulates cell adhesion and migration, induces V(H)-to-D(H)J(H) recombination, facilitates pre-B-cell receptor signaling and promotes development to the mature B-cell stage (PubMed:32612238). Repression of the cohesin- release factor WAPL causes global changes of the chromosomal architecture in pro-B cells to facilitate the generation of a diverse antibody repertoire (PubMed:32612238). {ECO:0000269|PubMed:10811620, ECO:0000269|PubMed:27181361, ECO:0000269|PubMed:32612238}. (Microbial infection) Plays an essential role in the maintenance of Epstein-Barr virus genome copy number within the host cell by promoting EBNA1/oriP-dependent binding and transcription (PubMed:31941781). Also participates in the inhibition of lytic EBV reactivation by modulating viral BZLF1 activity (PubMed:23678172). . This is the function of Ensembl gene identifier ENSG00000196092 (PAX5, paired box 5).