Decreased catalytic function with altered sumoylation of DNA topoisomerase I in the nuclei of scleroderma fibroblasts

Arthritis Res Ther. 2011 Aug 9;13(4):R128. doi: 10.1186/ar3435.


Introduction: Sumoylation is involved in nucleolus-nucleoplasm transport of DNA topoisomerase I (topo I), which may associate with changes of cellular and topo I functions. Skin fibroblasts of patients with systemic sclerosis (SSc) exhibit profibrotic cellular changes. The aims of this study were to examine the catalytic function and sumoylation of topo I in the nuclei of SSc fibroblasts, a major cell type involved in the fibrotic process.

Methods: Eleven pairs of fibroblast strains obtained from nonlesional skin biopsies of SSc patients and age/sex/ethnicity-matched normal controls were examined for catalytic function of nuclear topo I. Immunoprecipitation (IP)-Western blots were used to examine sumoylation of fibroblast topo I. Real-time quantitative RT-PCR was used to measure transcript levels of SUMO1 and COL1A2 in the fibroblasts.

Results: Topo I in nuclear extracts of SSc fibroblasts generally showed a significantly lower efficiency than that of normal fibroblasts in relaxing equivalent amounts of supercoiled DNA. Increased sumoylation of topo I was clearly observed in 7 of 11 SSc fibroblast strains. Inhibition of SUMO1 with SUMO1 siRNA improved the catalytic efficiency of topo I in the SSc fibroblasts. In contrast, sumoylation of recombinant topo I proteins reduced their catalytic function.

Conclusions: The catalytic function of topo I was decreased in SSc fibroblasts, to which increased sumoylation of topo I may contribute.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Biocatalysis*
  • Blotting, Western
  • Cell Nucleus / enzymology*
  • DNA Topoisomerases, Type I / metabolism*
  • Female
  • Fibroblasts / enzymology*
  • Humans
  • Immunohistochemistry
  • Immunoprecipitation
  • Male
  • RNA, Small Interfering
  • Real-Time Polymerase Chain Reaction
  • Reverse Transcriptase Polymerase Chain Reaction
  • Scleroderma, Systemic / enzymology*
  • Sumoylation
  • Transfection


  • RNA, Small Interfering
  • DNA Topoisomerases, Type I
  • TOP1 protein, human