Exploring novel functions of BACH2 in the acquisition of antigen-specific antibodies.

BACH2 [BTB (broad-complex, tramtrak and bric à brac) and CNC (cap 'n' collar) homolog 2] is known as a transcriptional repressor and broadly functions in regulating immune cell differentiation. Here, we focus on BACH2 function in B cells, where BACH2 was first shown to play an important role in the immune system. In B cells, BACH2 orchestrates the gene regulatory network that promotes class switch and affinity maturation of antibodies and simultaneously represses plasma-cell differentiation. In this context, BACH2 regulates gene expression by modulating chromatin organization, cooperatively with other transcription factors and chromatin regulators, such as IRF4 (interferon regulatory factor 4) and PC4 (positive coactivator 4), respectively. In addition, our recent observation raises the possibility that BACH2 has diverse functions, such as those in gene activation. Since dysfunction of BACH2 leads to the onset of human immune deficiencies, revealing new functions of BACH2 may give a cue to solve how BACH2 contributes to preventing these diseases.