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Determination of the Optimal Chromosomal Location(s) for a DNA Element in Escherichia coli Using a Novel Transposon-mediated Approach
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Determination of the Optimal Chromosomal Location(s) for a DNA Element in Escherichia coli Using a Novel Transposon-mediated Approach

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Cloning and characterization of the 5'-flanking sequence for the human DNA topoisomerase II beta gene

S W Ng1, Y Liu, L E Schnipper

  • 1Hematology/Oncology Division, Harvard Institutes of Medicine, Beth Israel Deaconess Medical Centre, East Campus, Boston, MA 02215, USA.

Gene
|January 13, 1998
PubMed

Insights

Investigating human topoisomerase IIbeta gene expression, this study identified key regulatory regions in its 5'-flanking sequence. These findings are crucial for understanding drug resistance mechanisms in cancer therapy.

Area of Science:

  • Molecular Biology
  • Genetics
  • Cancer Research

Background:

  • Mammalian cells possess two type II DNA topoisomerase isoforms, critical targets for numerous anticancer drugs.
  • Cellular sensitivity to topoisomerase II-targeting drugs is significantly influenced by the expression levels of these isozymes.

Purpose of the Study:

  • To explore the coordinated expression of topoisomerase II isoforms.
  • To elucidate the regulatory mechanisms governing gene expression in the context of drug resistance.
  • To clone and characterize the 5"-flanking sequence of the human topoisomerase IIbeta gene.

Main Methods:

  • Cloning and characterization of the 5"-flanking sequence of the human topoisomerase IIbeta gene.
  • Analysis of transcriptional start sites and GC content.
  • Transient expression assays with 5"- and 3"-deletions.
  • Gel mobility shift studies to identify protein-DNA interactions.

Main Results:

  • The 5"-flanking region of the topoisomerase IIbeta gene exhibits high GC content and lacks a TATA box, with two distinct transcriptional start sites.
  • Limited sequence homology exists between the 5"-flanking regions of topoisomerase IIbeta and topoisomerase IIalpha genes.
  • Deletion analyses identified critical regions for transcriptional regulation, including sequences within the first intron that enhance promoter activity.
  • Nuclear protein factors specifically bind to downstream elements, suggesting a role in transcriptional regulation.

Conclusions:

  • The study delineates regulatory elements controlling human topoisomerase IIbeta gene expression.
  • Understanding these mechanisms is vital for developing strategies to overcome drug resistance in cancer treatment.
  • The findings contribute to the broader understanding of topoisomerase II gene regulation and its implications in oncology.

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