The HXY box regulatory element modulates expression of the murine IA antigen-associated invariant chain in L fibroblasts.
The murine invariant chain (Ii) gene has been shown to be interferon-gamma (IFN-gamma)-inducible in a number of nonlymphoid cell types. In mouse L cells, steady-state levels of Ii mRNA are barely detectable in untreated cells but increase sharply upon IFN-gamma treatment. In IFN-gamma treated L cells, transcription starts 23, 28, 38, and 40 bases downstream of the TATA box. To identify cis-acting elements regulating expression of the Ii gene, reporter plasmids containing deletions of the Ii promoter have been constructed and transfected into mouse L cells. Deletion of the H box results in a 50-100% increase in basal expression. Deletion of both the H and X boxes increases basal expression by 200-300% above that seen in constructs containing all three elements. A 25% decrease in basal level expression is seen for constructs that lack the Y-box element when compared to constructs containing the Y-box element but not the H- and X-box elements. DNase I footprinting analysis demonstrates protection of the H, X, and Y boxes as well as a nonconserved region between the H and X boxes. Mobility-shift experiments detect a factor specifically interacting with the Y box. Although the H-, X-, and Y-box elements interact with nuclear protein and are regulatory elements in L cells, these elements do not appear to play a role in IFN-gamma induction suggesting that other regulatory mechanisms must account for IFN-gamma's induction of the Ii in L cells.
Kolk
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DP
Department of Zoology, Arizona State University, Tempe 85287.
Floyd-Smith
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G
D000818:Animals; D000944:Antigens, Differentiation, B-Lymphocyte; D001483:Base Sequence; D004247:DNA; D005786:Gene Expression Regulation; D000949:Histocompatibility Antigens Class II / Q000235:genetics*; D007371:Interferon-gamma / Q000502:physiology*; D007739:L Cells; D051379:Mice; D008969:Molecular Sequence Data; D010957:Plasmids; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid; D012689:Sequence Homology, Nucleic Acid; D014162:Transfection
D000944:Antigens, Differentiation, B-Lymphocyte; D000949:Histocompatibility Antigens Class II; C045084:invariant chain; D007371:Interferon-gamma; D004247:DNA