Evolution of human IgH3′EC duplicated structures: both enhancers HS1,2 are polymorphic with variation of transcription factor's consensus sites

The relevance of the polymorphisms in the HS1,2 enhancers is due to the variable number of binding sites for the transcription factors: NF-κB, CMYB, BSAP1/2, AP1/4, E47, MyoD and μE5 and thus to the possible influence of these variations on switch, production of Ig and on maturation of B cells.