A lipopolysaccharide-induced DNA-binding protein for a class II gene in B cells is distinct from NF-kappa B.
Class II (Ia) major histocompatibility complex molecules are cell surface proteins normally expressed by a limited subset of cells of the immune system. These molecules regulate the activation of T cells and are required for the presentation of antigens and the initiation of immune responses. The expression of Ia in B cells is determined by both the developmental stage of the B cell and by certain external stimuli. It has been demonstrated previously that treatment of B cells with lipopolysaccharide (LPS) results in increased surface expression of Ia protein. However, we have confirmed that LPS treatment results in a significant decrease in mRNA encoding the Ia proteins which persists for at least 18 h. Within the upstream regulatory region of A alpha k, an NF-kappa B-like binding site is present. We have identified an LPS-induced DNA-binding protein in extracts from athymic mice whose spleens consist predominantly of B cells. Binding activity is present in low levels in unstimulated spleen cells and is increased by LPS treatment. This protein binds to two sites in a regulatory region of the Ia A alpha k gene, one of which contains the NF-kappa B-like binding site. DNA fragments containing these sites cross-compete for protein binding. Analysis by DNase I footprinting identified a target binding sequence, named the LPS-responsive element. Although this target sequence contains an NF-kappa B-like binding site, competition with a mutant oligonucleotide demonstrated that bases critical for NF-kappa B binding are not required for binding of the LPS-inducible protein. Therefore, we hypothesized that this inducible protein represents a new mediator of LPS action, distinct from NF-kappa B, and may be one mechanism to account for the decrease in mRNA encoding the Ia proteins.
Gravallese
E M
EM
Department of Cancer Biology, Harvard School of Public Health, Boston, Massachusetts.
Boothby
M R
MR
Smas
C M
CM
Glimcher
L H
LH
D000818:Animals; D001402:B-Lymphocytes / Q000502:physiology*; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism; D004247:DNA / Q000032:analysis; D004268:DNA-Binding Proteins / Q000032:analysis* / Q000096:biosynthesis / Q000235:genetics; D003850:Deoxyribonuclease I; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis / Q000235:genetics*; D008070:Lipopolysaccharides / Q000494:pharmacology*; D051379:Mice; D008819:Mice, Nude; D008969:Molecular Sequence Data; D016328:NF-kappa B; D012313:RNA / Q000378:metabolism; D013154:Spleen / Q000166:cytology / Q000378:metabolism; D014157:Transcription Factors / Q000032:analysis* / Q000235:genetics
D004268:DNA-Binding Proteins; D000949:Histocompatibility Antigens Class II; D008070:Lipopolysaccharides; D016328:NF-kappa B; D014157:Transcription Factors; D012313:RNA; D004247:DNA; D003850:Deoxyribonuclease I