Identification of a Conserved Lipopolysaccharide-Plus-Interleukin-4-Responsive Element Located at the Promoter of Germ Line ε Transcripts

Abstract

Treatment of splenic B lymphocytes and certain B-lineage cell lines with the mitogen lipopolysaccharide (LPS) and the lymphokine interleukin-4 (IL-4) induces expression of germ line immunoglobulin C epsilon transcripts and class switching to the C epsilon gene. We show that LPS-plus-IL-4 induction of germ line epsilon transcripts (termed I epsilon transcripts) occurs at the transcriptional level in an Abelson murine leukemia virus-transformed pre-B-cell line. A 1.1-kb region of DNA surrounding the I epsilon promoter endows inducible transcription to a heterologous reporter gene stably transfected into these cells; such inducible expression depends on combined treatment with LPS and IL-4. Analyses of constructs transiently introduced into a B-cell lymphoma line demonstrated that LPS-plus-IL-4-inducible expression can be conferred by a 179-bp segment of DNA spanning the I epsilon transcriptional initiation site. Mutational analyses demonstrated that this expression depended on DNA sequences within a conserved region directly upstream from the I epsilon transcriptional initiation region. One nuclear protein that is constitutively expressed in normal B cells binds to the downstream end of the conserved sequence; its binding specificity correlates with the functional effect of several mutations. Two additional proteins, which are induced by IL-4 treatment of splenic B cells, bind to the transcription initiation sites of I epsilon. These proteins are indistinguishable in binding assays from proteins previously shown to bind an enhancer region of the class II major histocompatibility complex gene A alpha.

Selective Pharmaceutical Inhibition of PARP14 Mitigates Allergen-Induced IgE and Mucus Overproduction in a Mouse Model of Pulmonary Allergic Response

“…The induction of IgE is one of the first responses to IL-4 to be identified, and increased total IgE levels in humans are a hallmark of atopy. In parallel with its essential role in isotype switching to IgH Ce (9,10), this cytokine inhibits switching to Cg2a/c and levels of IgG2a/c (9). Accordingly, we analyzed the relative concentrations of Abs of these isotypes in Alternariachallenged mice and nonimmunized controls.…”

“…The choice of Ig H chain C region class during class switching in B cells is directed by IL-4, which is essential for generation of IgE, can promote IgG1, and suppresses selection of the Cg2a isotype for IgG2a production (9). The switch to IgE is directed by activation of the promoter for a noncoding germ line transcript termed Ie, which is inducible by IL-4 and initiated by binding of STAT6 to the IE promoter (10,11). Although normally present at very low levels, IgE is substantially increased by atopy and in allergic inflammation, during which it functions by cross-linking FcERI on mast cells and basophils (12).…”