The λ5-VpreB1 locus-a model system for studying gene regulation during early B cell development

The λ5 and VpreB genes encode the components of the surrogate light-chain, which forms part of the pre-B cell receptor. In mouse, the λ5 and VpreB1 genes of mouse are closely linked and coordinately regulated by a locus control region (LCR). Activation of the genes in pro-B cells depends on the combined effects of early B cell factor (EBF) and the E2A factors E12 and E47. Silencing of λ5 expression in mature B cells occurs through the action of Ikaros on the gene promoter where it may compete for binding of EBF and initiate the formation of a silent chromatin structure.