Effect of systemic lupus erythematosus antibodies against DNA on RNA synthesis

Inhibition of in vitro transcription by adenosine antibodies

Antibodies against adenosine markedly inhibited in vitro transcription in isolated BHK 21 nuclei in a dose-dependent manner. The inhibition was specific as it could be completely reversed by the addition of homologous hapten. Addition of RNA at low concentration reversed the inhibition, whereas excess DNA did not have any effect. Adenosine antibodies also inhibited in vitro transcription with calf thymus DNA and E. coli RNA polymerase. Antibodies that react with DNA but not with RNA such as anti-dpA, anti-dpC and anti-DNA failed to inhibit in vitro transcription in isolated nuclei as well as with calf thymus DNA and E. coli RNA polymerase. The results strongly indicate that the binding of adenosine antibodies to RNA is responsible for the inhibition of transcription.

Effects of antinuclear autoantibodies on RNA polymerase

DNA-dependent RNA polymerase was partially purified from wheat germ extract and tested for inhibition by antinuclear autoantibodies from the sera of patients with connective tissue diseases. The enzyme was inhibited by anti-DNA and by autoantibodies to the nuclear ribonucleoprotein nRNP. Autoantibodies to other ribonucleoproteins (Sm, Ro, La) did not cause inhibition. The enzyme preparation was shown to contain material with Ro and La antigenic activity but there was no nRNP or Sm detectable by immune precipitation. Previous work [3] has shown inhibition of prokaryotic (E. coli) RNA polymerase by anti-DNA, and our results show that the eukaryotic enzyme, in this case from wheat germ, is also inhibited. The results are consistent with the suggestion that inhibition by anti-DNA is due to template masking. Inhibition of RNA polymerase by antibodies to cellular ribonucleoprotein suggests that the antigen is in some way associated with the activity of the enzyme.