DNA binding sites 5' of the IgG1 switch region comprising IL4 inducibility and B cell specificity.

Immunoglobulin class switch recombination is directed to the same switch region on both chromosomes of a B cell by an as yet unknown mechanism. The cytokine interleukin 4 (IL4) targets recombination in activated B lymphocytes to the gamma 1 switch region (s gamma 1). Here we report two DNA-binding-proteins which bind to a sequence 5' of s gamma 1. One protein is B cell specific, while binding of the other one is induced by IL4. These two proteins bind to a region 700 bp upstream of the putative promoter region of the gamma 1 germline transcripts and may be involved in the process of recombination and/or transcription.