title: Lipopolysaccharide-mediated induction of RNA polymerase I activity and amount in murine B lymphocytes.
abstract: The effect of lipopolysaccharide on RNA polymerase I activity in primary cultures of murine B lymphocytes has been examined. In cells treated with mitogen for 48 h, the activity of RNA polymerase I was approximately 15 times greater than in control cells. In situ localization of RNA polymerase I using indirect immunofluorescence indicated that there was at least a 10-fold increase in the amount of this enzyme associated with nucleoli of 48 h mitogen-treated cells relative to control cells. Immunoblotting experiments demonstrated a similar increase in the concentration of the 190-kDa subunit bound to DNA; the concentrations of the other polymerase I-associated polypeptides did not correlate with rRNA synthesis. Assuming 1 mol of the 190-kDa polypeptide/mol of polymerase I, it was estimated that 2,300 and 30,000 molecules of enzyme were associated with rDNA in the unstimulated and stimulated B cell, respectively. Thus, an increased cellular concentration of the 190-kDa subunit of RNA polymerase I and its association with ribosomal DNA may be a crucial step in rRNA synthesis.
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000187:drug effects / Q000201:enzymology*; D002478:Cells, Cultured; D004275:DNA, Ribosomal / Q000378:metabolism; D004790:Enzyme Induction; D007163:Immunosorbent Techniques; D008070:Lipopolysaccharides / Q000494:pharmacology*; D051379:Mice; D008970:Molecular Weight; D012318:RNA Polymerase I / Q000096:biosynthesis*; D013936:Thymidine / Q000378:metabolism; D013997:Time Factors; D014529:Uridine / Q000378:metabolism
chemical_list: D004275:DNA, Ribosomal; D008070:Lipopolysaccharides; D012318:RNA Polymerase I; D013936:Thymidine; D014529:Uridine