The mouse immunoglobulin heavy-chain enhancer: effect on transcription in vitro and binding of proteins present in HeLa and lymphoid B cell extracts.

The ability of the mouse immunoglobulin heavy chain gene (IgH) enhancer to stimulate in vitro transcription from the adenovirus-2 major late promoter (Ad2MLP) has been investigated. In agreement with the in vivo cell-type specificity of this enhancer, a stimulation can be observed in BJA-B lymphoid B cell, but not in HeLa cell, extracts. Under identical conditions, the Simian virus 40 (SV40) enhancer stimulates transcription in both extracts to approximately the same extent. In addition we have found that a sequence, previously shown to inhibit transcription in vitro in HeLa cell extracts, is also inhibitory in B cell extracts. DNase I footprint and DMS-methylation protection experiments indicate that each cell type contains proteins which bind to specific sequences of the IgH enhancer. The relationship between the binding of these proteins and the preferential activity of the IgH enhancer in B cells is discussed.