Increment of DNA topoisomerases in chemically and virally transformed cells

Journal Article · Mon Feb 29 23:00:00 EST 1988 · Experimental Cell Research; (United States)

DOI:https://doi.org/10.1016/0014-4827(88)90267-4· OSTI ID:5322841

Crespi, M D; Mladovan, A G; Baldi, A ^[1]

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1. Instituto de Biologia y Medicina Experimental, Buenos Aires (Argentina)

The activities of topoisomerases I and II were assayed in subcellular extracts obtained from nontumorigenic BALB/c 3T3 A31 and normal rat kidney (NRK) cell lines and from the same cells transformed by benzo(a)pyrene (BP-A31), Moloney (M-MSV-A31) and Kirsten (K-A31) sarcoma viruses, and simian virus 40 (SV-NRK). The enzymatic activity of topoisomerase I was monitored by the relaxation of negatively supercoiled pBR322 DNA and by the formation of covalent complexes between {sup 32}P-labeled DNA and topoisomerase I. Topoisomerase II activity was determined by decatenation of kinetoplast DNA (k-DNA). It was found that nuclear and cytoplasmic type I topoisomerase specific activities were higher in every transformed cell line than in the normal counterparts. These differences cannot be attributed to an inhibitory factor present in A31 cells. When chromatin was treated at increasing ionic strengths, the 0.4 M NaCl extract showed the highest topoisomerase I specific activity. Spontaneously transformed A31 cells showed topoisomerase I activity similar to that of extracts of cells transformed by benzo(a)pyrene. Topoisomerase II specific activity was also increased in SV-NRK cells, as judged by the assay for decatenation of k-DNA to yield minicircle DNA.

• OSTI ID: 5322841
• Journal Information: Experimental Cell Research; (United States), Journal Name: Experimental Cell Research; (United States) Vol. 175:1; ISSN ECREA; ISSN 0014-4827
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMAL CELLS
ANIMALS
AROMATICS
BENZOPYRENE
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL EFFECTS
BODY
CELL TRANSFORMATIONS
CHROMATIN
CONDENSED AROMATICS
CONNECTIVE TISSUE CELLS
DAYS LIVING RADIOISOTOPES
DNA
ENZYME ACTIVITY
ENZYMES
FIBROBLASTS
HYDROCARBONS
ISOMERASES
ISOTOPES
KIDNEYS
KINETICS
LIGHT NUCLEI
MAMMALS
MICE
MICROORGANISMS
NUCLEI
NUCLEIC ACIDS
ODD-ODD NUCLEI
ONCOGENIC TRANSFORMATIONS
ONCOGENIC VIRUSES
ORGANIC COMPOUNDS
ORGANS
PARASITES
PHOSPHORUS 32
PHOSPHORUS ISOTOPES
RADIOISOTOPES
REACTION KINETICS
RODENTS
SOMATIC CELLS
VERTEBRATES
VIRUSES