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cDNA cloning of human DNA topoisomerase I. Catalytic activity of a 67. 7-kDa carboxyl-terminal fragment

Journal Article · · Proc. Natl. Acad. Sci. U.S.A.; (United States)
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cDNA clones encoding human topoisomerase I were isolated from an expression vector library (lambdagt11) screened with autoimmune anti-topoisomerase I serum. One of these clones has been expressed as a fusion protein comprised of a 32-kDa fragment of the bacterial TrpE protein linked to 67.7 kDa of protein encoded by the cDNA. Three lines of evidence indicate that the cloned cDNA encodes topoisomerase I. (i) Proteolysis maps of the fusion protein and human nuclear topoisomerase I are essentially identical. (ii) The fusion protein relaxes supercoiled DNA, an activity that can be immunoprecipitated by anti-topoisomerase I serum. (iii) Sequence analysis has revealed that the longest cDNA clone (3645 base pairs) encodes a protein of 765 amino acids that shares 42% identity with Saccharomyces cerevisiae topoisomerase I. The sequence data also show that the catalytically active 67.7-kDa fragment is comprised of the carboxyl terminus.

Research Organization:
Johns Hopkins Univ. School if Medicine, Baltimore, MD (USA)
OSTI ID:
6208342
Journal Information:
Proc. Natl. Acad. Sci. U.S.A.; (United States), Journal Name: Proc. Natl. Acad. Sci. U.S.A.; (United States) Vol. 85:8; ISSN PNASA
Country of Publication:
United States
Language:
English

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Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHEMICAL REACTIONS
CLONING
DAYS LIVING RADIOISOTOPES
DECOMPOSITION
DNA
DNA HYBRIDIZATION
DNA SEQUENCING
DNA-CLONING
ELECTROPHORESIS
ENZYME ACTIVITY
ENZYMES
HYBRIDIZATION
ISOMERASES
ISOTOPES
LIGHT NUCLEI
MAMMALS
MAN
NUCLEI
NUCLEIC ACIDS
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
PHOSPHORUS 32
PHOSPHORUS ISOTOPES
PRIMATES
PROTEOLYSIS
RADIOISOTOPES
RECOMBINANT DNA
STRUCTURAL CHEMICAL ANALYSIS
VERTEBRATES