Scl-70 is an antigen present on topoisomerase I, which is an ubiquitous intranuclear enzyme that mediates the twisting and untwisting of the DNA helix during gene transcription. It is a basic nuclear protein with a molecular weight of 70,000 daltons. Antibodies directed against Scl-70 usually give a nucleolar ANA pattern and are present exclusively in 70 % of patients with severe, diffuse forms of progressive systemic sclerosis, also known as scleroderma. Description: Calf Thymus. Alternative Names: Scleroderma protein, Scl70 protein, Scl-70, Scl- 70, Scl--70, Scl--70 protein, Scl- 70 protein