title: Association of an RNA polymerase III transcription factor with a ribonucleoprotein complex recognized by autoimmune sera.
abstract: RNA polymerase III transcription can be inhibited in vitro by two sera from patients with autoimmune diseases. The first serum, designated anti-SS-B (or La), has antibodies directed against a 50,000 dalton polypeptide that is part of a larger ribonucleoprotein complex. The second serum, designated anti-SpNo, recognizes a target antigen polypeptide of greater than 100,000 daltons as well as the SS-B antigen. Both sera selectively remove required transcription factors from the transcription extract, and inhibition can be rescued by the addition of a HeLa S100 extract to the depleted transcription system. The HeLa S100 extract was sequentially fractionated by ion-exchange chromatography on DEAE-cellulose and phosphocellulose. The high salt eluate from the latter column was also able to rescue the anti-SS-B inhibition as was the immunoaffinity-purified SS-B ribonucleoprotein complex isolated from HeLa, Xenopus or rabbit thymus. Immunoblots of the active fractions indicated that all contained the SS-B immunoreactive polypeptide, but probes of replica filters for DNA-binding suggested that the transcription factor is not the SS-B antigen but a 64,000 dalton polypeptide component of the antigen ribonucleoprotein complex. SS-B is itself an RNA-binding protein and could be shown to bind nascent 5S RNA transcripts in vitro. Differential ammonium sulfate precipitation and DNA cellulose chromatography has confirmed that a group of 64-68 K dalton polypeptides are components of the SS-B ribonucleoprotein complex associated with transcription factor activity.
mesh_terms: D001323:Autoantibodies; D001327:Autoimmune Diseases / Q000276:immunology; D004268:DNA-Binding Proteins / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000235:genetics*; D005796:Genes; D006367:HeLa Cells / Q000378:metabolism; D006801:Humans; D012320:RNA Polymerase III / Q000235:genetics* / Q000378:metabolism; D012261:Ribonucleoproteins / Q000378:metabolism*; D017411:Ribonucleoproteins, Small Nuclear; D014158:Transcription, Genetic
chemical_list: D001323:Autoantibodies; D004268:DNA-Binding Proteins; D012261:Ribonucleoproteins; D017411:Ribonucleoproteins, Small Nuclear; D012321:DNA-Directed RNA Polymerases; D012320:RNA Polymerase III