PT  - JOURNAL ARTICLE
AU  - Courtney E. W. Sulentic
AU  - Wei Zhang
AU  - Yong Joo Na
AU  - Norbert E. Kaminski
TI  - 2,3,7,8-Tetrachlorodibenzo-<em>p</em>-dioxin, an Exogenous Modulator of the 3′α Immunoglobulin Heavy Chain Enhancer in the CH12.LX Mouse Cell Line
AID  - 10.1124/jpet.103.059493
DP  - 2004 Apr 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 71--78
VI  - 309
IP  - 1
4099  - http://jpet.aspetjournals.org/content/309/1/71.short
4100  - http://jpet.aspetjournals.org/content/309/1/71.full
SO  - J Pharmacol Exp Ther2004 Apr 01; 309
AB  - Transcriptional regulation of the Ig heavy chain gene involves several regulatory elements, including the 3′α enhancer, which is composed of four distinct regulatory domains. DNA binding sites for several transcription factors, including B cell-specific activator protein, nuclear factor for immunoglobulin κ chain in B cells, and octamer have been identified within the 3′α enhancer domains and are believed to be important in regulating 3′α enhancer activity. We have identified an additional DNA binding motif, the dioxin-responsive element (DRE), which can contribute to 3′α enhancer regulation. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD), a known disrupter of B cell differentiation (i.e., decreased plasma cell formation, inhibition of μ heavy chain expression, and suppression of IgM secretion), induces binding of the aryl hydrocarbon receptor (AhR) nuclear complex to DREs. TCDD also induces AhR binding to the hypersensitive (hs)4 domain of the 3′α enhancer. Interestingly, TCDD enhances LPS-induced activation of the hs4 domain but profoundly inhibits LPS-induced activation of the complete 3′α enhancer. Furthermore, site-directed mutational analysis demonstrated that a DRE and κB element in the hs4 domain is modulated by TCDD in lipopolysaccharide-activated B cells. We propose that the AhR is a novel transcriptional regulator of the 3′α enhancer, which can mediate, at least in part, the effects of TCDD on the 3′α enhancer and its domains, putatively contributing to a marked suppression of IgM production. The American Society for Pharmacology and Experimental Therapeutics