title: Fluorescence enhancement of DNA-bound TO-PRO-3 by incorporation of bromodeoxyuridine to monitor cell cycle kinetics.
abstract: BACKGROUND
  The detection of DNA-incorporated bromodeoxyuridine (BrdUrd) in mammalian cells is a well-known and important technique to study cell cycle. The use of TO-PRO-3 for detection of BrdUrd substitution of DNA by dual-laser flow cytometry has been investigated.
  
  
  METHODS
  Fluorescence enhancement of TO-PRO-3 in BrdUrd-labeled cells is registered in combination with the fluorescence emission of the intercalating dye propidium iodide (PI) as a total DNA stain to give bivariate DNA/BrdUrd histograms. By the low concentration of only 0.3 mircoM TO-PRO-3, BrdUrd detection is optimized, and undisturbed total DNA content by PI can be detected as well. TO-PRO-3 is excited by a red HeNe laser and PI by an argon ion laser.
  
  
  RESULTS
  In order to understand the binding of TO-PRO-3, energy transfer from PI to TO-PRO-3 has been measured as well as the influence of an external DNA binding dye such as Hoechst 33258 with Adenine-Thymine (AT) binding specificity. Cell cycle studies of human SCL-2 keratinocytes and mouse 3T3 cells prove the method to be as generally applicable as the classical BrdUrd/Hoechst quenching technique, but without need for expensive ultraviolet laser excitation. No BrdUrd sensitivity could be found for the similar dyes TO-PRO-1 and YO-PRO-3, whereas TO-PRO-5 and YOYO-3 showed only very little sensitivity to BrdUrd labeling as compared with TO-PRO-3.
  
  
  CONCLUSIONS
  Cell cycle studies of mammalian cells can be done by dual-laser flow cytometry without the need for ultraviolet lasers by using the BrdUrd-dependent fluorescence enhancement of TO-PRO-3. Total DNA content can be measured simultaneously using PI.
authors.affiliation: GSF-National Research Center for Environment and Health, Flow Cytometry Group, Neuherberg, Germany. beisker@gsf.de
authors.forename: W
authors.initials: W
authors.lastname: Beisker
authors.forename: E M
authors.initials: EM
authors.lastname: Weller-Mewe
authors.forename: M
authors.initials: M
authors.lastname: Nüsse
mesh_terms: D016475:3T3 Cells / Q000166:cytology / Q000378:metabolism; D000818:Animals; D006690:Bisbenzimidazole / Q000737:chemistry; D001973:Bromodeoxyuridine / Q000378:metabolism*; D002232:Carbocyanines / Q000737:chemistry / Q000378:metabolism*; D002453:Cell Cycle; D002469:Cell Separation; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004735:Energy Transfer; D005434:Flow Cytometry / Q000379:methods*; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000378:metabolism*; D006801:Humans; D015603:Keratinocytes / Q000166:cytology / Q000378:metabolism; D051379:Mice; D013050:Spectrometry, Fluorescence / Q000379:methods; D013194:Staining and Labeling
chemical_list: D002232:Carbocyanines; D005456:Fluorescent Dyes; C098830:TO-PRO-3; D004247:DNA; D001973:Bromodeoxyuridine; D006690:Bisbenzimidazole