Regulatory elements necessary for termination of transcription within the Ig heavy chain gene locus

Previous experiments have shown that the extent of delta gene transcription during B cell development is regulated primarily at the transcriptional level. We have shown that deletion of a sequence located between the mu and delta coding regions in the Ig heavy chain locus where transcriptional termination has been previously mapped abrogates the termination. Restoration of termination requires reintroduction of this segment as well as sequence elements within the microM poly (A) site which cannot be substituted by the microS poly (A) site. Recognition of the termination site by non-lymphoid cells suggests that initiation of delta transcription in mature B lymphocytes requires the activation of an anti-termination mechanism not yet developed in early B cells.