Molecular regulation of MHC class III (C4 and factor B) gene expression in mouse peritoneal macrophages.
To study the molecular regulation of C4 and factor B synthesis in mouse peritoneal macrophages, mouse C4 cDNA clones isolated from an H-2d haplotype liver cDNA library, and a previously described mouse factor B cDNA clone, pBmB2 (9), were used to assess quantitative and qualitative differences in C4 and factor B mRNA in resident and elicited cells. The C4 clones that were isolated, pBmS2 (1 Kb) and pBmS10 (0.9 Kb), overlap and together span a 1.5 Kb coding region of mouse pro-C4, extending from the alpha-chain through the gamma-chain; four nucleotide substitutions are evident in comparing 316 bp of the sequence of clone pBmS10 to that of a previously described mouse C4 clone, pMLC4/w7-2 (23). By using these probes, Northern blot analysis of total cellular RNA revealed similar C4 mRNA levels in resident peritoneal macrophages from high-C4 (B10.A) and low-C4 (C3HeB) strains. Pulse and pulse-chase studies of C4 and factor B synthesis were performed on resident, starch-elicited, and thioglycollate-elicited peritoneal macrophages at two culture time periods, 0 to 9 and 24 to 33 hr, and total cellular RNA was isolated from each population at 4.5 and 28.5 hr of culture for Northern blot analysis of C4 and factor B mRNA content. The data demonstrate that as previously reported, C4 production decreases in elicited compared with resident macrophages and decreases with time in culture; however, factor B synthesis does not differ among resident and elicited cells and it increases with time in culture. The variations in C4 and factor B production by mouse peritoneal macrophages are not associated with alterations in C4 and factor B protein processing, catabolism, or secretion; rather, they are a function of differences in net amounts of C4 and factor B mRNA. These data provide direct evidence that the regulation of expression of these class III MHC genes in mouse peritoneal macrophages is a pretranslational event.
D000818:Animals; D001345:Autoradiography; D003001:Cloning, Molecular; D003101:Collodion; D003181:Complement C4 / Q000096:biosynthesis* / Q000235:genetics; D011415:Complement Factor B / Q000096:biosynthesis* / Q000235:genetics; D004247:DNA / Q000302:isolation & purification; D004587:Electrophoresis, Agar Gel; D004792:Enzyme Precursors / Q000096:biosynthesis*; D005260:Female; D006801:Humans; D008262:Macrophage Activation; D008264:Macrophages / Q000276:immunology / Q000378:metabolism* / Q000502:physiology; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D014176:Protein Biosynthesis; D012313:RNA / Q000302:isolation & purification
D003181:Complement C4; D004792:Enzyme Precursors; D012313:RNA; D003101:Collodion; D004247:DNA; D011415:Complement Factor B