Marton A, Marko B, Delbecchi L, Bourgaux P. Topoisomerase activity associated with polyoma virus large tumor antigen.
BIOCHIMICA ET BIOPHYSICA ACTA 1995;
1262:59-63. [PMID:
7772600 DOI:
10.1016/0167-4781(95)00050-q]
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Abstract
Polyomavirus (Py) large tumor antigen (LT) was produced in mammalian or insect cells infected with a suitable viral expression vector, and purified by a procedure combining immunoprecipitation with ion-exchange chromatography. Fractions containing the bulk of LT displayed a DNA-relaxing activity (LT-topo) which could be attributed neither to topoisomerase II (topo II) nor to topoisomerase I (topo I) encoded by the cell or the viral vector. On the one hand, LT-topo relaxed pBR322 DNA in a reaction which, unlike that characteristic of topo II, was ATP-independent and inhibited by camptothecin. On the other hand, serum from scleroderma patients which strongly inhibited calf thymus topo I had no effect on LT-topo, which absolutely required Mg2+ ions to relax DNA. Thus, LT-topo is either inherent to LT or belongs to a LT-bound enzyme similar to, but distinct from, topo I.
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