DIFFERENTIAL INTERACTIONS BETWEEN THE IMMUNOGLOBULIN HEAVY-CHAIN MU-INTRON AND 3'-ENHANCER

The immunoglobulin heavy chain 3' enhancer may be a novel type of a tr anscriptional regulation element in as much as its function is positio n dependent. We show that there are interactions between the mu intron and 3' enhancer which are differentially regulated depending on the d istance between the two elements. Thus, a transcriptional repression i s exerted by the 3' enhancer when juxtaposed to the intron enhancer. W hereas no or only modest synergism between the immunoglobulin mu intro n and 3' enhancer has been reported to date, we show here that the sti mulatory effect is substantially increased by extending the distance b etween the two enhancers. In our stable expression system, the mu intr on enhancer insulated the test gene from neighboring chromatin.