A new hypersensitive site, HS10, and the enhancers, E3' and Ed, differentially regulate Igκ gene expression.
The mouse Igκ gene locus has three known transcriptional enhancers: an intronic enhancer (Ei), a 3' enhancer (E3'), and a further downstream enhancer (Ed). We previously discovered, using the chromosome conformation-capture technique, that Ei and E3' interact with a novel DNA sequence near the 3' end of the Igκ locus, specifically in B cells. In the present investigation, we examined the function of this far downstream element. The sequence is evolutionarily conserved and exhibits a plasmacytoma cell-specific DNase I-hypersensitive site in chromatin, henceforth termed HS10 in the locus. HS10 acts as a coactivator of E3' in transient transfection assays. Although HS10(-/-) mice exhibited normal patterns of B cell development, they were tested further along with E3'(-/-) and Ed(-/-) mice for their Igκ expression levels in plasma cells, as well as for both allelic and isotype exclusion in splenic B cells. HS10(-/-) and Ed(-/-), but not E3'(-/-), mice exhibited 2.5-fold lower levels of Igκ expression in antigenically challenged plasma cells. E3'(-/-) mice, but not HS10(-/-) mice, exhibited impaired IgL isotype and allelic exclusion in splenic B cells. We have suggestive results that Ed may also weakly participate in these processes. In addition, HS10(-/-) mice no longer exhibited regional chromosome interactions with E3', and they exhibited modestly reduced somatic hypermutation in the Jκ-Cκ intronic region in germinal center B cells from Peyer's patches. We conclude that the HS10, E3', and Ed differentially regulate Igκ gene dynamics.
Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
Xiaorong
X
Zhou
Yougui
Y
Xiang
Xiaoling
X
Ding
William T
WT
Garrard
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D001483:Base Sequence; D015139:Blotting, Southern; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D002469:Cell Separation; D004742:Enhancer Elements, Genetic / Q000235:genetics* / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D005786:Gene Expression Regulation / Q000235:genetics* / Q000276:immunology*; D005803:Genes, Immunoglobulin / Q000235:genetics* / Q000276:immunology; D007136:Immunoglobulins / Q000096:biosynthesis / Q000235:genetics* / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
C014609:IgK; D007136:Immunoglobulins