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Definition of Topoisomerase

  • Medical Author:
    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Topoisomerase: A class of enzymes that alter the supercoiling of double-stranded DNA. (In supercoiling the DNA molecule coils up like a telephone cord, which shortens the molecule.) The topoisomerases act by transiently cutting one or both strands of the DNA. Topoisomerase type I cuts one strand whereas topoisomerase type II cuts both strands of the DNA to relax the coil and extend the DNA molecule.

The regulation of DNA supercoiling is essential to DNA transcription and replication, when the DNA helix must unwind to permit the proper function of the enzymatic machinery involved in these processes. Topoisomerases serve to maintain both the transcription and replication of DNA.

Aside from topoisomerases I and II, there are more discovered topoisomerases. Topoisomerase III may regulate recombination while topoisomerase IV regulates the process of segregating newly replicated chromosomes from one another.

Reviewed on 12/21/2018

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