The Igκ 3'-enhancer triggers gene expression in early B lymphocytes but its activity is enhanced on B cell activation

Abstract

Igκ gene expression is controlled by two enhancers, one located within the major intron (Ei) and the other located downstream of C(κ) (E3'). Whereas loss of E3' has previously been shown to diminish κ expression, we show here that a rearranged κ transgene lacking Ei is well expressed, even at the pre-B cell stage. This suggests that E3' alone might be sufficient to give properly regulated transcription throughout B cell development. Indeed, we show that a transgene composed of a β-globin reporter linked to E3' is expressed in a B cell-specific manner, becoming activated at the late pro-B to pre-B cell stage but with dramatically enhanced activity on B cell activation. Thus, E3' becomes active as a transcription enhancer at the stage when V(κ)-J(κ) rearrangement is being initiated and is sufficient to yield an expression pattern in a linked reporter gene similar to that of fully rearranged κ genes.